Optical spectroscopy and transport studies of tunnelling processes and hot electron relaxation in GaAs-AlGaAs and GaAs-AlAs single barrier heterostructures

We report a series of optical and transport experiments on GaAs-AlGaAs and GaAs-AlAs single barrier tunnel structures. We show that electroluminescence (EL) experiments on such structures enable tunneling mechanisms and hot carrier relaxation processes to be determined with spectroscopic precision. Tunnelling mechanisms are contrasted for direct gap AlGaAs and indirect gap AlAs barriers. By combining the EL studies with complementary transport measurements we are able to obtain a full description of tunnelling through indirect gap barrier structures, demonstrating in a very clear way the importance of both longitudinal and transverse valleys in the tunnelling process.