DEFECTS IN MOVPE GROWN ZNSE ON GAAS STUDIED BY DEEP-LEVEL TRANSIENT SPECTROSCOPY

The defect related properties of MOVPE grown ZnSe layers on GaAs were investigated by electrical measurements. Ditertiarybutylselenide and d imethylzinc-triethylamine were used as precursors for the ZnSe growth. In order to carry out nitrogen doping trimethylsilylacide triallylami ne and bisditrimethylsilylamido-zinc were used as N precursors. The N doping was also performed by N-2 de-plasma. Current-voltage (I-V) and capacitance-voltage (C-V) measurements reveal n-type behavior in all c ases. The N-D - N-A net doping concentration amounts to 10(16) - 10(17 ) cm(-3). An electron trap center with a thermal activation energy in a range of 0.30 to 0.33 eV and a capture cross section of about 10(-15 ) cm(2) was determined by means of deep level transient spectroscopy a nd isothermal capacitance transient spectroscopy measurements. This tr ap was detectable in all N-doped samples except in the case of a TMSiN doped sample. Since an electron trap center with comparable features has been also found in n-type single crystalline ZnSe and, as reported by other groups, also in n-type MBE ZnSe, it is assumed, that the exi stence of this state is related to a native defect in the as grown lay er.