Wurtzite boron nitride properties

Executive summary

1. Thermal expansion of wurtzite boron nitride is approx. 1.5 lower than that of hexagonal boron nitride. Which means higher stability of wurtzite boron nitride coating layer under high temperatures (<2000 °C = 3632 °F);
2. Thermal conductivities of wurtzite crystal, parallel and perpendicular to the axis, are identical. Which means higher stability of thermal properties in comparison to other heat resistant materials, including such forms of boron nitride as hexagonal and cubic (zinc blende). 
3. Wurtzite boron nitride has a wider band gap, higher thermal conductivity, and larger spontaneous polarization,  which represent a potential for manufacturing of advanced electronic devices, e.g. in strain engineering and  developing deep UV emitters.

The research

 Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It has the following 4 crystal structures: 

- BN_w (wurtzite structure), similar to lonsdaleite rare hexagonal polymorph of carbon but slightly softer than the cubic form;
- BN_cub (cubic BN, zinc blende structure), softer than diamond, but its thermal and chemical stability is superior;
- BN_hex (hexagonal BN), the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products;
- rhombehedral. 

Research of  properties of the first 3 crystal structures is presented below.

BN_hex is stable under normal conditions. BN_hex (Hexagonal, also known as a-BN) with the structure similar to graphite is known for more than a century. Many properties of hexagonal BN are highly anisotropic and depend on the growth method. In many cases, the different values of BN_hex physical parameters given reflect the differences in material properties of hexagonal BN grown by different methods.

BN_cub is metastable under normal conditions. BN_cub (Zinc blende modification , also known as cubic or sphalerite or b-BN) was first synthesized in 1957 using the technique similar to that used for diamond growth. Now powders of cubic boron nitride  are commercially available.

The BN_w phase is metastable under all conditions. BN_w (Wurtzite structure, also known as g-BN) was first synthesized in 1963. Typically, BN crystals with wurtzite symmetry are very small (fraction of microns), are highly defective, and contain other phases. 
   BN_w (wurtzite boron nitride) and BN_cub (cubic boron nitride)  have a similar bond length, elastic moduli, ideal tensile and shear strength,  which suggests the two would demonstrate similar indentation strengths, around 50 GPa; diamond is 70–150 GPa.
   Traditionally, wurtzite boron nitride (BN_w) is produced by transforming hexagonal boron nitride (BN_hex), the most stable crystal form of boron nitride.  You can buy wurtzite boron nitride powder, obtained by shock compression (explosion) of hexagonal boron nitride  here.  
  Wurtzite boron nitride is   a promising III-V group wide-band-gap material for advanced electronic devices because it has many properties superior to Gallium nitride (GaN) and Aluminium nitride (AlN), such as a wider band gap, higher thermal conductivity, and larger spontaneous polarization.

Basic Parameters for Cubic/Zinc Blende crystal structure

		Remarks	Referens
Crystal structure	Zinc Blende
Group of symmetry	T2d — F43m
Number of atoms in 1 cm3
Debye temperature	1700 K
Density	3.4870 g cm-3 3.450 g cm-3	X-ray	Soma et al. (1974) Rumyantsev et al. (2001)
Lattice constant, a	3.6157(10) A	X-ray	Sohno et al. (1974)
Melting point, Tm	2973° C		Wentorf (1957)
Bulk modulus	400 GPa	300 K
Hardness	9.5	on the Mohs scale
Surface hardness	4500 kg mm-2	300 K
Second order elactic moduli, c11	7.120 ·1012 dyn cm-2	300 K, interpolated from measured values of other III-IV compound	Steigmeier (1963)
Phonon wevenumber vLO	1305(1) cm-1	300 K, Raman	Sanjurjo et al. (1983)
Phonon wevenumber vTO	1054.7(6) cm-1	300 K, Raman	Sanjurjo et al. (1983)

Brillouin zone of the face centered cubic lattice, the Bravais lattice of the diamond and zincblende structures.

		Remarks	Referens
Energy gaps, Eg	6.1÷6.4 eV	300 K	Rumyantsev et al. (2001)
Energy gaps, Egind G15v-X1c	6.4(5) eV	300 K, UV absorption; other data in range 6...8eV	Chrenko (1974)
	6.99 eV 8.6 eV	calculated, Band structure calculated, Band structure	Huang & Ching (1985) Prasad & Dubey (1984)
Energy gaps, Eg,dir G15v-G1c	14.5 eV 10.86 eV 9.94 eV	300 K, reflecsivity calculated, Band structure calculated, Band structure	Philipp & Taft (1962) Prasad & Dubey (1984) Huang & Ching (1985)
Effective electron mass  ml	0.752 mo	calculated from band structure data	Huang & Ching (1985)
Effective electron mass       (longitudinal) ml       (transversal) mt	0.35mo 0.24mo	1.2mo 0.26mo	Xu & Ching et al. (1991)
Effective hole masses (heavy) mh	0.375 mo 0.962 mo	|| [100] || [111]	Madelung (1991)
Effective hole masses (heavy) mlp	0.150 mo 0.108 mo	|| [100] || [111]	Madelung (1991)
Effective hole masses mh      in the direction G  K	m1 ~=3.16 m2 ~=0.64 m3 ~=0.44	300 K	Xu & Ching et al. (1991)
in the direction G  X	0.55mo	300 K	Xu & Ching et al. (1991)
in the direction G  L	m1 ~=0.36 m2 ~=1.20	300 K	Xu & Ching et al. (1991)
Electron affinity	4.5 eV	300 K	Rumyantsev et al. (2001)

		Remarks	Referens
Dielectric constant (static)	7.1	300 K, infrared reflectivity	Gielisse et al.(1967)
Dielectric constant (high frequency)	4.5 4.46	300 K, infrared reflectivity	Gielisse et al.(1967) Rumyantsev et al. (2001)
Refractive index, n	2.17	300 K, wavelegth 0.589mm	Gielisse et al.(1967)
Optical phonon energy	~130 meV	300 K	Rumyantsev et al. (2001)
Bulk modulus	400 GPa
Debye temperature	1700 K
Melting point, Tm	2973° C	also see Thermal properties. Phase diagrams.	Wentorf (1957)
Specific heat	~0.6 J g-1°C -1
Thermal conductivity     experimentally achieved	7.4 W cm-1 °C -1
theoretically estimated	~13 W cm-1 °C -1
Thermal expansion, linear	1.2·10-6 °C -1

		Remarks	Referens
carrier concentration and mobility:
n µ	1015 cm-3 0.2 cm2/Vs	500 K, polycrystalline material, type of carrier not determined	Bam et al.(1976)
n µ	1014 cm-3 4 cm2/Vs	900 K, mobility increases exponentially with rising temperature between 500 K and	Bam et al.(1976)

---

Basic Parameters for Hexagonal crystal structure

		Remarks	Referens
Crystal structure	Hexagonal
Group of symmetry	D6c-P63mmc
Number of atoms in 1 cm3
Debye temperature	400 K
Density	2.18 g cm-3 2.0-2.28 g cm-3		Madelung (1991) Rumyantsev et al. (2001)
Lattice constant, a	2.5040 A 2.5-2.9 A	297 K 300 K	Lynch et al. (1966) Rumyantsev et al. (2001)
Lattice constant, c	6.6612 A 6.66 A	297 K 300 K	Lynch et al. (1966) Rumyantsev et al. (2001)
Decomposition temperature, Tdec	2600(100) K		Janaf Thermochemical Tables (1965)
Bulk modulus	36.5 GPa	300 K
Hardness	1.5	on the Mohs scale
Phonon wevenumber, v	49 cm-1	E2g, zone center Raman mode	Hoffman et al. (1966)
	770 cm-1	A2u, infrared active mode
	1367 cm-1	E2g, zone center Raman mode
	1383 cm-1	E1u, infrared active mode

Brillouin zone of the hexagonal lattice.

		Remarks	Referens
Energy gaps, Eg	5.2(2) eV 3.2...5.8 eV	300 K, reflectance range of experimental data temperature dependence of resistivity	Hoffmann et al. (1984)
	4.0...5.8 eV	300 K	Rumyantsev et al. (2001)
Energy gaps, Eg dir	7.1 eV		Carpenter & Kirby (1982)
Effective electron mass ml      in the direction M   G      in the direction M  L	0.26mo 2.21mo	300 K	Xu & Ching et al. (1991)
Effective hole masses mh      in the direction K   G      in the direction M   G      in the direction M  L	0.47mo 0.50mo 1.33mo	300 K	Xu & Ching et al. (1991)
Electron affinity	4.5 eV	300 K	Rumyantsev et al. (2001)

		Remarks	Referens
Dielectric constant (static)	=5.06 =6.85	|| to c axis _ to c axis	Geick et al.(1966)
Dielectric constant (high frequency)	4.10 4.95	parallel to c axis perpendicular to c axis for 300 K; see also Optical properties. Dielectric functions	Geick et al.(1966)
	= 2.2; =4.3	300 K	Rumyantsev et al. (2001)
Dielectric constant (static)	7.1	300 K, infrared reflectivity	Gielisse et al.(1967)
Dielectric constant (high frequency)	4.5 4.46	300 K, infrared reflectivity	Gielisse et al.(1967) Rumyantsev et al. (2001)
Refractive index, n	1.65 1.65 2.13	BN- film perpendicular to c axis parallel to c axis	Takahashi et al.(1981) Ishii et al. (1983) Ishii et al. (1983)
Debye temperature	400 K
Bulk modulus	36.5 GPa
Melting point		see Termal properties. Phase diagrams.
Decomposition temperature, Tdec	2600(100) K		Janaf Thermochemical Tables (1965)
Specific heat	~0.8 J g-1°C -1
Thermal conductivity    parallel to the c axis     perpendicular to the c axis	=<0.3 W cm-1 °C -1 =<6 W cm-1 °C -1		Rumyantsev et al. (2001)
Thermal expansion, linear     parallel to the c axis     perpendicular to the c axis	38·10-6 °C -1 -2.7·10-6 °C -1

---

Basic Parameters for Wurtzite, Zinc Blende & Hexagonal crystal structure at 300 K

Crystal structure	Wurtzite	Zinc Blende	Hexagonal
Group of symmetry	C46v-P63mc	T2d-F43m	D6c-P63mmc
Density	3.4870 g cm-3	3.450 g cm-3	2.0-2.28 g cm-3
Bulk modulus	400 GPa	400 GPa	36.5 GPa
Debye temperature	1400 K	1700 K	400 K
Melting point		see Thermal properties. Phase diagrams.
Specific heat	~0.75 J g-1°C -1	~0.6 J g-1°C -1	~0.8 J g-1°C -1
Density	3.4870 g cm-3	3.450 g cm-3	2.0-2.28 g cm-3
Hardness on the Mohs scale		9.5	1.5
Surface hardness	3400 kg mm-2	4500 kg mm-2
Dielectric constant (static)	=6.8 ; =5.1	7.1	=6.85 ; =5.06
Dielectric constant (high frequency)	~=  = 4.2-4.5	4.46	=4.3;  = 2.2
Infrared refractive index	2.05	2.1	1.8
Lattice constant, a	2.55 A	3.615 A	2.5-2.9 A
Lattice constant, c	4.17 A		6.66
Effective electron mass       (longitudinal) ml       (transversal) mt	0.35mo 0.24mo	1.2mo 0.26mo
(in the direction M   G)      (in the direction M  L)			0.26mo 2.21mo
Effective hole masses mh      in the direction G  K	0.88mo	m1 ~=3.16 m2 ~=0.64 m3 ~=0.44
in the direction G  A      in the direction G  M	1.08mo 1.02mo
in the direction G  X		0.55mo
in the direction G  L		m1 ~=0.36 m2 ~=1.20
in the direction K   G      in the direction M   G      in the direction M  L			0.47mo 0.50mo 1.33mo
Effective hole massesof dencity of states mv	~=1.0mo
Electron affinity	4.5 eV	4.5 eV	4.5 eV
Thermal conductivity     experimentally achieved     theoretically estimated		7.4 W cm-1 °C -1 ~13 W cm-1 °C -1
parallel to the c axis     perpendicular to the c axis			=<0.3 W cm-1 °C -1 =<6 W cm-1 °C -1
Thermal expansion, linear		1.2·10-6 °C -1
Thermal expansion, linear     parallel to the c axis     perpendicular to the c axis	2.7·10-6 °C -1 2.3·10-6 °C -1		38·10-6 °C -1 -2.7·10-6 °C -1
Optical phonon energy	~130 meV	~130 meV

Crystal structure	Wurtzite	Zinc Blende	Hexagonal
Energy gaps, Eg	4.5-5.5 eV	6.1...6.4 eV	4.0...5.8 eV
Conduction band
Energy separation EG	8.5 eV	8.5-10 eV	9 eV
Energy separation EM	6.6 eV
Energy separation EL		>12 eV
Energy separation EA			10 eV
Effective conduction banddensity of states	1.5x1019 cm-3	2.1x1019 cm-3
Effective valence banddensity of states	2.6x1019 cm-3	2.6x1019 cm-3
Breakdown field		(2...6)x 106 V cm-1	(1...3)x 106 V cm-1
Mobility electrons		=<200 cm2 V-1 s-1
Mobility holes		=<500 cm2 V-1 s-1
Diffusion coefficient electrons		=<5 cm2 s-1
Diffusion coefficient holes		=<12 cm2 s-1
Effective valence banddensity of states	2.6x1019 cm-3	2.6x1019 cm-3

Thermal properties

Basic parameters

Zinc Blende crystal structure

		Remarks	Referens
Bulk modulus	400 GPa
Debye temperature	1700 K
Melting point, Tm	2973° C	also see Phase diagrams for BN.	Wentorf (1957)
Specific heat	~0.6 J g-1°C -1
Thermal conductivity     experimentally achieved     theoretically estimated	7.4 W cm-1 °C -1 ~13 W cm-1 °C -1
Thermal expansion, linear	1.2·10-6 °C -1

Thermal properties for Hexagonal crystal structure

		Remarks	Referens
Debye temperature	400 K
Bulk modulus	36.5 GPa
Melting point		see Phase diagrams for BN.	Solozhenko (1994) and Solozhenko et al.(1998)
Decomposition temperature, Tdec	2600(100) K		Janaf Thermochemical Tables (1965)
Specific heat	~0.8 J g-1°C -1
Thermal conductivity     parallel to the c axis     perpendicular to the c axis	=<0.3 W cm-1 °C -1 =<6 W cm-1 °C -1		Rumyantsev et al. (2001)
Thermal expansion, linear     parallel to the c axis     perpendicular to the c axis	38·10-6 °C -1 -2.7·10-6 °C -1

Wurtzite, Zinc Blende & Hexagonal crystal structure at 300 K

Crystal structure	Wurtzite	Zinc Blende	Hexagonal
Bulk modulus	400 GPa	400 GPa	36.5 GPa
Melting point		see Phase diagrams for BN.
Specific heat	~0.75 J g-1°C -1	~0.6 J g-1°C -1	~0.8 J g-1°C -1
Thermal conductivity     experimentally achieved     theoretically estimated		7.4 W cm-1 °C -1 ~13 W cm-1 °C -1
parallel to the c axis     perpendicular to the c axis			<0.3 W cm-1 °C -1 <6 W cm-1 °C -1
Thermal expansion, linear		1.2·10-6 °C -1
Thermal expansion, linear     parallel to the c axis     perpendicular to the c axis	2.7·10-6 °C -1 2.3·10-6 °C -1		38·10-6 °C -1 -2.7·10-6 °C -1

---

Thermal conductivity

	BN, Zinc Blende. Temperature dependence of thermal conductivity for different samples. Slack (1973), Makedon et al. (1972)
	BN, Zinc Blende. Temperature dependences of the thermal conductivity of undoped and Se doped before and after annealing at 900-1000 K. 1- undoped Zinc blende BN; 2-4 - Se doped Zinc blende BN Selenium concentration:   2 -- 2.4 x 1018 cm-3, before annealing;   3 -- 2.4 x 1018 cm-3, annealed;   4 -- 1019 cm-3, annealed Shipilo et al. (1986)

The highest thermal conductivity achieved for single-crystal zinc blende BN is 7.4 W cm^-1 K^-1 [Novikov et al. (1983)].

	BN, Hexagonal. Thermal conductivity perpendicular to the c axis versus temperature of three samples deposited at different temperatures. Duclaux et al. (1992)
	BN, Hexagonal. Thermal conductivity perpendicular to the c axis versus temperature of highly oriented samples. Sichel et al. (1976)
	BN, Hexagonal. Thermal conductivity perpendicular to the c axis as a function of temperature for two samples. Simpson & Stuckes (1971)
	BN, Hexagonal. Thermal conductivity parallel to the c axis as a function of temperature for two samples. Simpson & Stuckes (1971)

---

Temperature dependence of the specific heat

Wurtzite BN . Temperature dependence of the specific heat.

BN, Wurtzite. Temperature dependence of the specific heat. Gorbunov et al. (1988); see also Sirota & Kofman (1976) and Inaba & Yoshiasa (1997). The abnormality with extremum at 21 K is caused by the presence of the ordered point defects system in the lattice for two samples. Solozhenko (1994)

At 420 K < T < 980 K, the specific heat C_p of Wurtzite BN can be approximated as
C_p= 48.35x (T² ·(T²- 8.37xT+ 68306)^-1)² (J/Kmol) Solozhenko (1994).

Zinc Blende BN . Temperature dependence of the specific heat.

	BN, Zinc Blende. Temperature dependence of the specific heat at low temperatures (single crystal). Solozhenko et al. (1987); see also Sirota & Kofman (1976).
	BN, Zinc Blende. Temperature dependence of high temperature specific heat according to different authors. Lyusternik and Solozhenko (1992).

At 300 < T < 1100 K, the specific heat C_p of Zinc Blende BN can be approximated as
C_p= 48.4x (T² · (T²- 9.71xT+ 60590)^-1)² (J/Kmol) Lyusternik and Solozhenko (1992).

Hexagonal BN . Temperature dependence of the specific heat.

BN, Hexagonal. Temperature dependence of specific heat. Gorbunov et al. (1988); see also Sichel et al. (1976)

At 1300 < T < 2200 K, the specific heat C_p of can be approximated as
C_p= 52.48 - 9.42·10^-4 x T - 64877 x T^-2 (J/Kmol) Solozhenko (1994).

---

Linear thermal expansion coefficient.

	BN, Wurtzite. Linear thermal expansion coefficient of parallel (curve 1) and perpendicular (curve 2) to c axis. Kolupayeva et al. (1986).
	BN, Hexagonal. Linear thermal expansion coefficient. Slack & Bartram (1975).
	BN, Zinc Blende. Linear thermal expansion coefficient Top curve, in a direction parallel to the c axis; bottom curve, in a direction perpendicular to the c axis. Yates et al. (1975). See also Belenkii et al. (1985).

---

Thermal expansion at different pressure

BN, Hexagonal. Thermal expansion at different pressure: circles, 1.6 GPa; squares, 5.0 GPa; triangles, 7.1 GPa. Solid and open symbols are used for the directions parallel and perpendicular to c axis, respectively. Solozhenko & Peun (1997).

---

Phase diagrams

	Phase diagrams for BN. 1, Bundy-Wentorf's diagram; 2, Equilibrium diagram; , h-BN <=> c-BN boundary line. Solozhenko (1994)
	Equilibrium phase diagram of BN. 1 is hexagonal-zinc blende BN liquid triple point; 2 is hexagonal-wurtzite BN liquid metastable triple point; a) line of hexagonal-wurtzite BN metastable equilibrium; b) metastable beam of hexagonal BN melting curve; c) line of wurtzite BN metastable melting . Solozhenko et al.(1998)

Band structure and carrier concentration

All band structure calculations lead to an indirect gap structure, the conduction band minima being situated at X.

---

Basic Parameters for Zinc Blende crystal structure

		Remarks	Referens
Energy gaps, Eg	6.1...6.4 eV	300 K	Rumyantsev et al. (2001)
Energy gaps, Eg ind G15v-X1c	6.4(5) eV	300 K, UV absorption; other data in range 6...8eV	Chrenko (1974)
	6.99 eV 8.6 eV	calculated, Band structure calculated, Band structure	Huang & Ching (1985) Prasad & Dubey (1984)
Energy gaps, Eg dir G15v-G1c	14.5 eV 10.86 eV 9.94 eV	300 K, reflecsivity calculated, Band structure calculated, Band structure	Philipp & Taft (1962) Prasad & Dubey (1984) Huang & Ching (1985)
Electron affinity	4.5 eV	300 K	Rumyantsev et al. (2001)

Conduction band
Energy separation EG	8.5-10 eV	300 K	Rumyantsev et al. (2001)
Energy separation EL	>12 eV	300 K
Effective conduction banddensity of states	2.1·1019 cm-3	300 K
Effective valence banddensity of states	2.6·1019 cm-3	300 K

Basic Parameters for Hexagonal crystal structure

		Remarks	Referens
Energy gaps, Eg	5.2(2) eV 3.2...5.8 eV	300 K, reflectance range of experimental data temperature dependence of resistivity	Hoffmann et al. (1984)
	4.0...5.8 eV	300 K	Rumyantsev et al. (2001)
Energy gaps, Eg dir	7.1 eV		Carpenter & Kirby (1982)
Electron affinity	4.5 eV	300 K	Rumyantsev et al. (2001)

		Remarks	Referens
Conduction band
Energy separation EG	9 eV	300 K	Rumyantsev et al. (2001)
Energy separation EM	>12 eV	300 K
Energy separation EL	10 eV	300 K
Energy separation EA	10 eV	300 K
Effective conduction banddensity of states	2.1x1019 cm-3	300 K
Effective valence banddensity of states	2.1x1019 cm-3	300 K

Basic Parameters for Wurtzite, Zinc Blende & Hexagonal crystal structure at 300 K

Crystal structure	Wurtzite	Zinc Blende	Hexagonal
Energy gaps, Eg	4.5-5.5 eV	6.1...6.4 eV	4.0...5.8 eV
Conduction band
Energy separation EG	8.5 eV	8.5-10 eV	9 eV
Energy separation EM	6.6 eV
Energy separation EL		>12 eV
Energy separation EA			10 eV
Effective conduction banddensity of states	1.5x1019 cm-3	2.1x1019 cm-3
Effective valence banddensity of states	2.6x1019 cm-3	2.6x1019 cm-3

 

---

Band structure for Zinc Blende BN

	BN, cubic. Band structure calculated with the LCAO-method, including ionicity and fitting of APW results at high symmetry points. Prasad & Dubey (1984)
	BN, cubic. Band structure calculated with the LCAO-method, ab intitio calculation. Hoffmann et al. (1984)
	BN, zinc blende(cubic). Band structure. Important minima of the conduction band and maxima of the valence band. 300K; Eg =6.1-6.4 eV; Ep= 8.5-10eV; EL > 12 eV For details see Rodriguez-Hernandez et al. (1995) and Ferhatet al. (1998)

Brillouin zone of the face centered cubic lattice, the Bravais lattice of the diamond and zincblende structures.

Band structure for Hexagonal BN

BN, hexagonal (graphite-like). Band structure. Important minima of the conduction band and maxima of the valence band. The energy gaps between the top of the valence band and H, M, K, and L valleys of the conduction band are of the same order of magnitude. The energies of the valence band maxima are very close in the points K, H, and M of Brillouin zone. 300K; Eg =4.0-5.8 eV; EA= 10eV; EG = 9 eV For details see Yong-Nian Xu and Ching (1991), Zunger al. (1976) and Taylor and Clarke (1997)

BN, Hexagonal(graphite-like). Band structure calculated with the tight binding method. Hoffmann et al. (1984)

A band structure calculation [Catellani et al. (1984)] taking into account interlayer interaction proposes an indirect gap of 3.9 eV between a valence band maximum at H and a conduction band minimum at M as well as additional interlayer conduction bands with minimum at the zone center

Brillouin zone of the hexagonal lattice.

Band structure for Wurtzite BN

BN, Wurtzite. Band structure. Important minima of the conduction band and maxima of the valence band. 300K; Eg =4.5-5.5 eV; EM= 6.6eV; EG = 8.5 eV For details see Christersen and Gorczyca (1994) and Yong-Nian Xu and Ching(1991).

---

Effective Density of States in the Conduction Band, N_c

Only the calculated data available for the values of electron effective masses for all types of BN crystals (see Effective Masses ).

Wurtzite	Nc ~= 4.82 x 1015 · (mcd/m0)3/2· T3/2 (cm-3) ~= 2.8 x 1015 x T3/2(cm-3)
Zinc blende	Nc ~= 4.82 x 1015 · (mcd/m0)3/2· T3/2 (cm-3) ~= 4.1 x 1015 x T3/2(cm-3)

Effective Density of States in the Valence Band, N_v

Only the calculated data available for the values of hole effective masses for all types of BN crystals. These calculations are fairly inaccurate. As a crude estimate, the effective density of states in the valence band, N_v:
N_v ~= 5.0 x 10¹⁵ · T^3/2 (cm^-3)
could be used for all crystal modifications of BN (see Effective Masses ).

Dependence on Hydrostatic Pressure

Pressure dependence of the energy gap of zinc blende BN. (Onodera et al., 1993)

		Referens
zinc blende BN	dEg/dP = 3.0 meV/GPa	Kim et al. (1996)
wurtzite BN	dEg/dP = 3.8 meV/GPa	Kim et al. (1996)

Effective Masses and Density of States:

Electrons

Effective Masses for Zinc Blende BN

The surface of equel energy are ellipsoids.

		Remarks	Referens
Effective electron mass  ml	0.752 mo	calculated from band structure data	Huang & Ching (1985)
Effective electron mass       (longitudinal) ml       (transversal) mt	1.2mo 0.26mo		Xu & Ching et al. (1991)

Effective mass of density of states in one valley of conduction band [Xu & Ching et al. (1991)]
m_c=(m_l·m_t²)^1/3=0.43m_o
Effective mass of conductivity [Xu & Ching et al. (1991)] : m_cc=3(1/m_l+ 2/m_t)^-1 ~= 0.35m_o
Effective mass of density of states for all valleys of conduction band [Xu & Ching et al. (1991)]: m_cd ~= 0.9m_o

Effective Masses for Hexagonal crystal BN

		Remarks	Referens
Effective electron mass ml      in the direction M G      in the direction M L	0.26mo 2.21mo	300 K	Xu & Ching et al. (1991)

Effective Masses for Wurtzite BN

The surface of equel energy are ellipsoids.

		Remarks	Referens
Effective electron mass       (longitudinal) ml       (transversal) mt	0.35mo 0.24mo		Xu & Ching et al. (1991)

Effective mass of density of states in one valley of conduction band [Xu & Ching et al. (1991)]
m_c=(m_l·m_t²)^1/3=0.27m_o
Effective mass of conductivity [Xu & Ching et al. (1991)] : m_cc~=3(1/m_l+ 2/m_t)^-1 ~= 0.27m_o
Effective mass of density of states for all valleys of conduction band [Xu & Ching et al. (1991)]: m_cd~=0.7m_o

Holes

Effective Masses for Zinc Blende BN		Remarks	Referens
Effective hole masses (heavy) mh	0.375 mo 0.962 mo	|| [110] || [111]	Madelung (1991)
Effective hole masses (heavy) mlp	0.150 mo 0.108 mo	|| [110] || [111]	Madelung (1991)
Effective hole masses mh      in the direction G  K	m1 ~= 3.16 mo m2 ~= 0.64 mo m3 ~= 0.44 mo	300 K	Xu & Ching et al. (1991)
in the direction G X	0.55mo	300 K	Xu & Ching et al. (1991)
in the direction G L	m1 ~= 0.36 mo m2 ~= 1.20 mo	300 K	Xu & Ching et al. (1991)

Effective Masses for Hexagonal crystal BN		Remarks	Referens
Effective hole masses mh      in the direction K G      in the direction M G      in the direction M L	0.47mo 0.50mo 1.33mo	300 K	Xu & Ching et al. (1991)

Effective Masses for Wurtzite BN		Remarks	Referens
Effective hole masses mh      in the direction G K      in the direction G A      in the direction G M	0.88mo 1.08mo 1.02mo	300 K	Xu & Ching et al. (1991)

Donors and Acceptors

Zinc Blende (cubic) BN:

Ionization energies of donors	Si    C   S	0.24 eV 0.28-0.41eV 0.05 eV	Wentorf (1957), Mishima et al. (1987), Taniguchi et al. (1993), Gubanov et al. (1997)
Ionization energies of acceptor	Be	0.19 eV	Wentorf (1957), Mishima et al. (1987), Taniguchi et al. (1993), Gubanov et al. (1997)

Hexagonal(graphite-like) BN:

Ionization energies of donors	0.7...1.5 eV	Wentorf (1957), Mishima et al. (1987), Taniguchi et al. (1993), Gubanov et al. (1997)
Ionization energies of acceptor	=< 1.5 eV	Wentorf (1957), Mishima et al. (1987), Taniguchi et al. (1993), Gubanov et al. (1997)

Optical properties

---

Zinc Blende crystal structure

		Remarks	Referens
Dielectric constant (static)	7.1	300 K, infrared reflectivity	Gielisse et al.(1967)
Dielectric constant (high frequency)	4.5 4.46	300 K, infrared reflectivity	Gielisse et al.(1967) Rumyantsev et al. (2001)
Refractive index, n	2.17	300 K, wavelegth 0.589mm	Gielisse et al.(1967)
Infrared refractive index	~=2.1	300 K, Infrared	Rumyantsev et al. (2001)
Optical phonon energy	~130 meV	300 K	Rumyantsev et al. (2001)

Hexagonal crystal structure

		Remarks	Referens
Dielectric constant (static)	=5.06 =6.85	|| to c axis  perp. to c axis	Geick et al.(1966)
Dielectric constant (high frequency)	4.10 4.95	parallel to c axis perpendicular to c axis for 300 K; see also Dielectric functions	Geick et al.(1966)
	= 2.2; =4.3	300 K	Rumyantsev et al. (2001)
Dielectric constant (static)	7.1	300 K, infrared reflectivity	Gielisse et al.(1967)
Dielectric constant (high frequency)	4.5 4.46	300 K, infrared reflectivity	Gielisse et al.(1967) Rumyantsev et al. (2001)
Refractive index, n	1.65 1.65 2.13	BN- film perpendicular to c axis parallel to c axis	Takahashi et al.(1981) Ishii et al. (1983) Ishii et al. (1983)
Infrared refractive index	~=1.8	300 K, Infrared	Rumyantsev et al. (2001)

BN, hexagonal. Ordinary and extraordinary dielectric functions e2 vs. wavelength and photon energy in the range 13---30eV (b). Mamy et al. (1983)

Wurtzite, Zinc Blende & Hexagonal crystal structure at 300 K

Crystal structure	Wurtzite	Zinc Blende	Hexagonal
Infrared refractive index	~=2.05	~=2.1	~=1.8

---

Optical properties of Wurtzite, Zinc Blende & Hexagonal crystal

	BN, hexagonal. Ordinary and extraordinary dielectric functions e2 vs. wavelength and photon energy in the range 5--9eV Mamy et al. (1981)
	BN, hexagonal. Ordinary and extraordinary dielectric functions e2 vs. wavelength and photon energy in the range 13--30eV Mamy et al. (1981)
	BN, zinc blende. Refractive index n versus photon energy Miyata et al. (1989)
	BN. Refractive index n versus wavenumber. 1 -- Zinc blende 2 -- Hexagonal BN. Stenzel et al. (1996)
	BN, Wurtzite. Reflectance R as a function of photon energy for two samples. 1, 500oC annealed; 2, 100o C annealed (nanoscale powder compacted into dense solid under high pressure). Yixi et al. (1994)
	BN, Zinc Blende. Reflectance R as a function of photon energy. Miyata et al. (1989)
	BN, Hexagonal. Reflectance R as a function of wavelength . Zunger et al. (1976)
	BN, Hexagonal. Reflectance R as a function of wavelength . Hoffman et al. (1984)
	BN, Wurtzite. The absorption coefficient as a function of photon energy for two samples. 1, 500oC annealed; 2, 100oC annealed (nanoscale powder compacted into dense solid under high pressure). Yixi et al. (1994)
	BN, Zinc Blende. The absorption coefficient versus photon energy. Miyata et al. (1989)
	BN, Zinc Blende. The absorption coefficient versus photon energy at different hydrostatic pressures. The energies shown by arrows are defined as indirect band gaps. Onodera et al. (1993)
	BN, Zinc Blende. The absorption coefficient versus wavenumber in the infrared. Chrenko et al. (1974)
	BN, Hexagonal. The absorption coefficient versus wavelength. 300K. Zunger et al. (1976)
	BN, Hexagonal. The absorption coefficient versus wavelength at 4.2 K and 600 K. Zunger et al. (1976)

Buy wurtzite boron nitride powder
Buy cubic boron nitride powder