Thermodynamic model of low temperature metalorganic chemical vapor deposition of GaN

Abstract

A thermodynamic model is developed to explain low temperature metalorganic chemical vapor deposition of GaN. The two stage epitaxial processes taking into account the physisorbed states on (0001) A and B planes are considered. The physisorbed Ga coverage of both GaN planes is presented as the function of the pressures, temperature, and efficiency of ammonia decomposition. The thermodynamic affinities of each stage of the growth runs are described. The formation conditions of the GaN wurtzite and zinc-blende modifications are discussed. The model developed was applied to estimate the thermodynamic characteristics of low temperature metalorganic chemical vapor deposition of GaN. It is quantitatively shown that the considered growth conditions allows formation of the stable and metastable GaN modifications in the same epitaxial run.

Sublimation and Vapor Deposition

“…For example, when titanium tetrabromide (TiBr 4 ) is used as a precursor to deposit titanium film, the chemical reaction is accomplished in the following steps (Mazumder and Kar, 1995): GaAs GaCI(g) + (1/4)As4(g) = GaAs(s) + HCI(g) Sivaram (1995) GaAs(g) + HCI(g) =GaCI(g) + 1/4(As 4 (g)) + 1/2(H 2 (g)) 700-850°C Sivaram (1995) GaAs Ga(CH 3 ) 3 +AsH 3 = GaAs+3CH 4 Al(CH 3 ) 3 +AsH 3 = AlAs+3CH 500-800°C Ueda (1996) GaN Ga(g) + NH 3 = GaN(s) + (3/2)H 2 (g) 650°C Elyukhin et al (2002) Ge(s) GeH 4 =Ge(s) + 2H 2 Herring (1990) Si SiH 4 (g)=Si(s)+2H 2 (g) >600 o C (polysilicon) >850-900 o C (single crystal) Herring (1990) SiC Si(CH 3 ) 4 (g)=SiC(s)+3CH 4 (g) 700-1450 °C Sun et al (1998) Sivaram (1995) TiO 2 TiCl 4 (g)+O 2 (g)=TiO 2 (S)+2Cl 2 (g) Jakubenas et al (1997) TiN TiCl 4 (g)+2H 2 (g)+(1/2)N 2 (g)=TiN(s)+4HCl(g ) 900°C Mazumder and Kar (1995) CVD reactors may operate at atmospheric reduced pressure (APCVD)which varies from 0.1 to 1 atm -or at low pressure (LPCVD). It depends on availability of a volatile gaseous chemical that can be converted to solid film through some thermally activated chemical reaction.…”