II-VI/III-V heterostructures: Epilayer-on-epilayer structures

The molecular beam epitaxy (MBE) and the microstructural, optical, and electrical characterization of two technologically important heterojunctions, the CdTe/InSb and the ZnSe/GaAs, are described. The II-VI/III-V heterointerface is formed by the epitaxial growth of each layer in either separate MBE growth chambers, or by each layer growth occurring in a single growth chamber. For the case where separate growth chambers are used, the active interface is preserved by employing passivation techniques, or by transferring the sample between growth chambers in an ultrahigh vacuum transfer module. The aforementioned growth approaches allow for the formation of an ‘epitaxial’ heterojunction, to be utilized as an active part of a heterojunction device. The CdTe/InSb heterointerface is approximately lattice matched (<0.05% mismatch), and is motivated by possible device applications provided by InSb quantum wells. The low temperature growth of InSb quantum wells is achieved by the use of an antimony cracking oven to provide Sb₂ molecules for the growth. No clear indication of mixed interfacial layers of In₂Te₃ is observed by Raman spectroscopy or transmission electron microscopy. The ZnSe/GaAs heterointerface, having a 0.25% lattice constant mismatch, has potential for use in passivation of GaAs devices. The highly resistive, stoichiometric ZnSe is employed as an insulator in two GaAs device configurations: a field effect transistor structure and a metal-insulator-semiconductor capacitor. Electrical characteristics of the ZnSe/GaAs interface provide evidence of the electrical integrity, with measurements of the interface state density resulting in numbers comparable to those reported for the (A1, Ga)As/GaAs interface.