Epitaxial InGaAs/InAlAs/AlAs Structures for Heterobarrier Varactors with Low Leakage Current

The quality of heteroboundaries and optimal conditions for epitaxial growth are critical parameters for obtaining low leakage currents of heterobarrier varactors in the InGaAs/InAlAs/AlAs material system. Grown by molecular-beam epitaxy, three-barrier heterobarrier varactor structures adjacent to InAlAs/AlAs/InAlAs barrier layers by additional mismatched InGaAs layers subjected to compressive stress show, under optimal epitaxy conditions, extremely low levels of leakage current density (not more than 0.06 A/cm2 at a voltage of 5 V and 85°C) with relatively thin AlAs inserts (with a thickness of 2 nm).