Novel GaAs/AlAs tunnel structures as microwave detectors

摘要

We have designed (using a specially developed simulation package) some novel GaAs/AlAs tunnel structures with highly asymmetric current-voltage (I-V) characteristics for use as microwave detectors. The asymmetry arises from having unequal spacer regions either side of a single AlAs tunnel barrier. Recent designs have a microwave performance at 9.4 GHz which matches a zero-bias Schottky diode in terms of voltage sensitivity and dynamic range, but with a much better ($EQ weaker) temperature dependence. The new diodes also out-perform existing germanium back diodes in their voltage sensitivity and dynamic range, although the variation of sensitivity with temperature is not quite as small; it is expected however that this gap can be closed. The main competition for the new diodes is expected to come from the recently developed planar-doped-barrier detector (PDB) diodes, which combine the high sensitivity and dynamic range of the Schottky diode with a somewhat weaker variation with temperature. However, our diodes are still expected to have a weaker temperature dependence, and they would seem to be more easily and cheaply manufactured due to the problems associated with control over the p$PLU doping spike in a PDB diode: we have successfully made structures by both MBE and MOCVD. In this paper, we describe the design of our diodes and demonstrate the above points with detailed graphs of d.c. and microwave performance for one MBE-grown structure and one MOCVD-grown structure.