The effect of a field-independent polarization discontinuity on heterojunction characteristics

A new utilization of the basic semiconductor heterojunction is proposed which is based on the mechanism of a field-independent polarization discontinuity P at the interface of a p-n heterojunction. Variations in P yield changes in the space-charge regions and the associated barrier voltages at the interface. By proper choice of the heterojunction parameters, the barrier voltage change can be made approximately linear with P over a finite range. The barrier voltage variation modulates the I-V characteristic of the heterojunction for the case of a positive reverse interface barrier, and modifies the C-V relation in all cases. Typical values are calculated for the properties of the general polarization discontinuity heterojunction, and of a strain-sensitive unit which utilizes a piezo-electric interaction. For the latter, the calculated differential sensitivities are 10²to 10³and 10⁴to 10⁵volts per unit strain for the barrier voltage and device output voltage, respectively. This output voltage sensitivity is 1 to 2 orders of magnitude larger than that available in piezoresistive strain gages. This device concept has potential in a variety of technically important areas ranging from mechanical instrumentation to sequentially excited light-emitting arrays. The heterojunction configuration is compatible with both evaporated and epitaxial semiconductor technology, and materials with the necessary combination of physical properties are represented among the well-known II-VI and III-V compounds.