| abstract |
A semiconductor device, such as vertical-cavity surface emitting laser (VCSEL) or a superlattice-heterojunction bipolar transistor (SL-HBT) 10, incorporates a superlattice region 16 in series with the emitter 14 or another active region. The superlattice region 16 provides a non-linear response to a sufficiently high level of device current counteracting thermal runaway. This protects the device from damaging levels of current. The device 10 may be a radio-frequency SL-HBT with performance equivalent to that of a conventional heterojunction bipolar transistor. If there is a array of devices, e.g. a multi-finger bipolar transistor or an array of VCSELS, the invention prevents current-hogging by a single device. Application to FETs, HEMTs, PHEMTs, MESFETs, HFETs and diodes is also mentioned. |