Study of gallium arsenide surfaces

A.c. and d.c. field effect experiments have been performed on etched n and p-type GaAs samples. On (111) surfaces of n-type GaAs, quasi-equilibrium measurements are possible at very low frequencies, and a surface conductance minimum can be observed. From this the existence of acceptor levels, to a large extent bulk states, can be concluded. From optical measurements three levels (1·09, 0·88, 0·73 eV) can be deduced at room temperature. A second quasi-equilibrium situation with much larger relative conductance changes exists at high frequencies (around 8 kc s) where the surface appears to be n-type. The slow bulk trapping has been investigated more directly with d.c. measurements, and results concerning trapping times and temperature dependences are presented. On p-type samples with (110) surfaces, evidence for slow surface states, which are ambientdependent, similar to those of Ge surfaces, has been found. © 1964.