Evaluation of molecular beam epitaxially grown AlGaAs/GaAs heterojunctions for bipolar transistor with InGaAs emitter contact layer

Molecular beam epitaxially grown AlGaAs/GaAs heterojunctions were characterized by isothermal capacitance transient spectroscopy to study the performance of bipolar transistors with lattice-mismatched InGaAs emitter contact layer. A deep level around 0.48 eV is found to be a recombination center in the N-AlGaAs/p+-GaAs junction which might be induced by oxygen. Anomalous signals are also observed under an isothermal condition where the edge of the depletion layer reaches the graded InGaAs/AlGaAs heterointerface. Two electron traps with activation energies of 0.26 and 0.62 eV are identified as dominant factors.