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Characteristics and Properties

Band structure and carrier concentration of Gallium Phosphide (GaP)

Band structure and carrier concentration

Basic Parameters
Temperature Dependences
Dependences on Hydrostatic Pressure
Energy Gap Narrowing at High Doping Levels
Effective Masses
Donors and Acceptors

Basic Parameters

Energy gap	2.26 eV
Energy separation Eo (Γ1c - Γ15ν)	2.78 eV
Energy spin-orbital splitting	0.08 eV
Intrinsic carrier concentration	2 cm-3
Effective conduction band density of states	1.8·1019 cm-3
Effective valence band density of states	1.9·1019 cm-3

Band structure and carrier concentration of GaP. Important minima of the conduction band and maxima of the valence band. 300 K Eg = 2.26 eV EL = 2.6 eV Eo = 2.78 eV Eso = 0.08 eV

Temperature Dependences

Temperature dependence of the direct energy gap.

E_g=2.34-6.10^-4·[T²/(T+460)] (eV),
where T is temperature in degrees K (0 < T < 1200),
(Panish and Casey [1969]).

Temperature dependence of the direct band gap E_o

E_o=2.866-0.108·[coth(164/T)-1] (eV),
where T is temperature in degrees K (0 < T < 300),
(Takizawa [1983]).

Effective density of states in the conduction band

N_c≈3.4·10¹⁵·T^3/2 (cm^-3)

Effective density of states in the valence band

N_n≈3.6·10¹⁵·T^3/2 (cm^-3)

	The temperature dependence of the intrinsic carrier concentration.
	Fermi level versus temperature for different concentrations of shallow donors and acceptors.

Dependences on Hydrostatic Pressure

,
where P is pressure in kbar;
(Ves et al. [1985]).

Energy Gap Narrowing at High Doping Levels

Energy gap narrowing versus donor (curve 1) and acceptor (curve 2) doping density, T= 300 K, (calculated according Jain et al. [1990]).

For n-type GaP

ΔE_g = 10.7·10^-9·N_d^1/3 + 3.45·10^-7·N_d^1/4 + 9.97·10^-12·N_d^1/2 (eV)
(Jain et al. [1990]).

For p-type GaP:

ΔE_g = 12.7·10^-9·N_a^1/3 + 5.85·10^-7·N_a^1/4 +3.90·10^-12·N_a^1/2 (eV)
(Jain et al. [1990]).

Effective Masses

Electrons:
The surfaces of equal energy are ellipsoids (X-valley)
	ml = 1.12mo
	mt = 0.22mo
Effective mass of density of states
mc=(9mlmt2)1/3	mc=0.79mo
Effective mass of conductivity	mcc=0.35mo
For Γ-valley	mΓ = 0.09mo
For L-valley	ml = 1.2mo
	mt = 0.15mo
Holes:
Heavy	mh = 0.79mo
Light	mlp = 0.14mo
Effective mass of density of states	mv = 0.83mo

Donors and Acceptors

Ionization energies of shallow donors (eV)

Sp	Sep	Tep	Lip	GeGa	SiGa	SnGa	LiGa
0.107	0.105	0.093	0.091	0.204	0.085	0.072	0.061

(Dean [1973), Kopilov and Pikhtin [1978]).

Ionization energies of shallow acceptors (eV)

Gep	Cp	Sip	BeGa	CdGa	MgGa	ZnGa
0.265	0.0543	0.210	0.0566	0.1022	0.0599	0.0697

(Dean [1973]).

Most important deep levels

Impurity	Position in the forbidden gap
Op(donor)	Ec - 0.89 (eV)
Cr (acceptor)	Ec - 1.2 (eV)
	Ec - 0.5 (eV)
Radiative centers(Baegh and Dean[1976])
N	Ev + 0.008 (eV)
ZnGa - Op	Ec - 0.3 (eV)
Capture cross section for electrons to neutral Zn-O complex (at 300 K)	σn~(1.5÷4.5)·10-16 (cm2)
Capture cross section for holes to negative Zn-O complex (at 77 K):	σp ~ 5·10-17 (cm2
CdGa - Op	Ec - 0.40 (eV)
Mg - O	Ec - 0.14 (eV)

(Dean and Henry [1968], Clerjaud et al. [1981]).

 

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