Analysis of silicon incorporation into the GaAs melt from the quartz boat during the single crystal growing with horizontal Bridgman method

수평 Bridgman 법에 의한 GaAs 단결정 성장시 석영 보트(boat)로부터의 Si 유입에 대한 분석

The mechanism of silicon incorporation has been analyzed for the boat-grown GaAs crystals on the basis of phase equilibrium in the Ga and As system. Comparison was made between silicon concentrations calculated from the thermodynamics of incorporation reaction and carrier concentrations measured from van der Pauw method. For the 1-T HB(single temperature zone horizontal Bridgman) crystals, calculated concentrations were 5.3 ×10 15 (atoms/cm3), measured as 9.8 ×10 15(/cm3) at the seed part. They were calculated to be 1.1 ×10 16(atoms/cm3) and measured as 1.5 ×10 16(/cm3) for the 2-T(double temperature zone) HB crystals. On the other hand, it was found to be closer between the calculated and measured silicon concentrations for the VGF(vertical gradient freeze) crystals, which were grown within half the run time compared with 1-T or 2-T HB method.

석영 boat를 반응용기로 쓰는 수평 Bridgman 법에서, GaAs 단결정에 유입되는 Si 농도를 Ga-As 계의 상평형에 근거한 열역학적 평형을 가정하여 성장방법 별로 계산하였고, Hall 측정에 의한 전자 농도 측정치와 비교하였다. 단일 온도대역 수평 Bridgman(1-T HB) 법의 경우 Si 농도의 계산치가 5.3 ×10 15(atoms/cm3)인데 비해 실험치는 9.8 ×10 15(/cm3) 이었고, 이중 온도대역 수평 Bridgman(2-T HB) 법에서는 계산치가 1.1 ×10 16(atoms/cm3), 측정치가 1.5 ×10 16(/cm3) 인 것으로 각각 나타났다. 한편 1-T나 2-T HB 법에 비하여 성장시간이 절반 정도인 VGF(vertical gradient freeze) 방법의 경우 이론치와 실험치가 비교적 일치 하였고 그 값은 (6∼8) ×10 15 (atoms/cm3)인 것으로 나타났다.