DETECTION OF DEEP LEVELS AND COMPENSATION MECHANISM IN UNDOPED, LIQUID-ENCAPSULATED CZOCHRALSKI N-TYPE GAAS

Undoped n-GaAs with a 300 K resistivity between 10(-1) and 10(8) OMEGA cm (electron concentration between 1 x 10(7) and 5 x 10(15) cm -3) grown in quartz crucibles by the liquid-encapsulated Czochralski (LEC) technique was investigated by thermally stimulated current (TSC), temperature-dependent Hall effect (TDH), and deep-level transient spectroscopy (DLTS). Using Schottky contacts the TSC method could be extended to medium-resistivity samples. The strongly varying electron concentrations are correlated to varying TDH activation energies. The correlation between the donors dominating the electrical equilibrium properties and the electron traps detected by TSC and DLTS is discussed. Medium-deep and deep levels are present in this LEC material in such high concentrations that they must be taken into account in the compensation mechanism.