GaP - Gallium Phosphide

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 Eo1c - 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.

Eg=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 Eo

Eo=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

Nc≈3.4·1015·T3/2 (cm-3)

Effective density of states in the valence band

Nn≈3.6·1015·T3/2 (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

Eqn,
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

ΔEg = 10.7·10-9·Nd1/3 + 3.45·10-7·Nd1/4 + 9.97·10-12·Nd1/2 (eV)
(Jain et al. [1990]).

For p-type GaP:

ΔEg = 12.7·10-9·Na1/3 + 5.85·10-7·Na1/4 +3.90·10-12·Na1/2 (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]).