Band Bending and Passivation Studies of GaAs Grain Boundaries

The zero‐bias band‐bending properties of grain boundary (g‐b) interfaces showing pronounced rectifying characteristics in polycrystalline GaAs were investigated both experimentally and theoretically. A strongly rectifying g‐b presents a potential barrier to the majority carrier leading to a large g‐b resistance R B . R B for individual g‐b's was determined by passing a constant current normal to the g‐b and monitoring the voltage drop, as a function of temperature, associated with the thermionic current. The band‐bending e Φ b , as a function of donor density N D , was obtained from a plot of the activation energy k B ( TR B ) vs. (1/ T ). A theoretical fit of the e Φ b vs. N D curve gave a dominant density of defect acceptor states at the g‐b interface: σ 1 = 5.2 × 10 11 / cm 2 at 0.41 eV and σ 2 = 9.0 × 10 11 / cm 2 at 0.90 eV below E c . These acceptor levels have been tentatively identified with the dangling bonds of A‐ and B‐type dislocations which normally occur at III–V compound‐semiconductor g‐b's. In addition, the use of potassium as a grain boundary passivating dopant is discussed. After diffusing K into the g‐b, a lower R B and reduction in the g‐b rectifying properties were noted.