DEPENDENCE OF DEEP LEVEL CONCENTRATION ON NONSTOICHIOMETRY IN MOCVD GAAS

Investigations have been made of deep levels in undoped GaAs crystals grown by metal organic chemical vapor deposition (MOCVD) on liquid encapsulated Czochralski (LEC) GaAs wafers. The dependence of electron trap level EL2 concentration and a lattice constant on nonstoichiometric composition of epitaxial GaAs crystals has been clarified by changing the mole flux ratio of arsine (AsH//3) to trimethyl gallium (TMG), left bracket ASH//3 right bracket / left bracket TMG right bracket , from ten to eighty. The dependence of EL2 concentration and a lattice constant on left bracket AsH//3 right bracket / left bracket TMG right bracket strongly suggests that an interstitial arsenic atom or group of interstitial arsenic atoms leads to development of EL2.