Electrical properties of indium doped GaAs layers grown by MBE

The use of indium doping in bulk grown GaAs has recieved much attention as a way of reducing the defect concentration as revealed by the etch pit density. In this work we report similar indium doping studies in MBE grown GaAs. n-Type GaAs has been grown with indium concentrations up to 0.1 at % and at substrate temperatures from 540 to 580°C. We have made measurements of the free carrier concentration using C-V and Hall measurements, Hall mobility, 4 K photoluminescence and deep level concentrations. For a given substrate growth temperature, the most obvious effect of indium doping is to give an increase in the measured free electron concentration. This correlates with a higher 77 K mobility which suggests a reduction in the degree of compensation. The indium also leads to an order of magnitude reduction in the intensity of deep level-related PL features. The use of indium at normal GaAs growth temperature (580°C) is made difficult by re-evaporation. However, indium doping does allow the growth of high electrical quality GaAs at reduced temperatures, which is of particular benefit for the growth of GaAs on top of single crystal aluminium layers.