Characterization of In sub x Ga sub (1-x) As/GaAs Strained Heterostructures: Comparison of Dislocation Structure with Carrier Mobility and Device Results

We have grown by molecular beam epitaxy, GaAs/In sub x Ga sub (1-x) /GaAs heterostructures with In sub x Ga sub (1-x) As layers 20nm thick and varying x from 0.00 to 0.50 in 0.05 steps. The In sub x Ga sub (1-x) As layers were doped p-type and exhibited Hall mobilities which increased from x=0.00 to a maximum of 55.3 cm sup 2 V sup (-1) sec sup (-1) at x=0.10, and subsequently declined with increasing x. Heterojunction bipolar transistors fabricated from these structures also showed a maximum current gain of 190 at x=0. 1. At higher concentrations, misfit dislocations degrade device performance. We discuss the nature and density of these dislocations, and show that they are responsible for carrier concentration at high densities.