Ballistic electron emission microscopy of strained and relaxed In0.35Ga0.65As/AlAs interfaces

We report here our investigations upon both strained and relaxed In0.35Ga0.65As/AlAs interfaces using the ballistic electron emission microscopy (BEEM) and current–voltage (I–V) techniques. Six samples, of different InGaAs thickness and doping density, were grown by molecular beam epitaxy and were designed to assess the importance of strain relaxation/dislocations in barrier formation. In the heavily dislocated situation (thicker InGaAs film) the obtained barrier most likely resulted from Fermi level pinning. However, this was obviously not the case for both the pseudomorphic and lightly dislocated situations (thinner InGaAs films). It was also noted that the measured barriers varied more widely over space in the lightly dislocated layer than that in the pseudomorphic case and that the simultaneously obtained topographic and BEEM images points to a better interface in the pseudomorphic layer than that in the partially relaxed situation.