Effect of interfacial dopant layer on transport properties of high purity InP

Temperature dependent Hall measurements were used to investigate the role of unintentional interfacial dopant layers on the electrical properties of high purity InP. Secondary ion mass spectroscopy was used to measure the level of Si contamination present in several samples at the substrate-epilayer interface. We show that the presence of interfacial dopant gives rise to two layer conduction whose temperature dependence mimics the freezeout behavior expected for a deep donor. However, the magnetic field dependence of the Hall data at low temperatures shows the expected behavior for the two layer model, including an order of magnitude variation in the apparent sheet concentration and Hall mobility over the range from 0.1 to 0.6 T at 77 K. We show that the true bulk mobility and carrier concentration can be accurately determined in samples with high interfacial contamination by performing Hall measurements at several magnetic fields at 77 K. (C) 1996 American Institute of Physics.