Outage probability analysis for microcell mobile radio systems with cochannel interferers in Rician/ - Electronics Letters

the mobility result is comparable to that achieved in other ZDEG structures where the GaAs layer has been grown on the modulation doped layer of AlGaAs.” In future designs the precise collector barrier profile will be altered to increase this transfer efficiency. Even allowing for possible parallel conduction in the collector barrier at room temperature in our present structure, the base-base resistance of 800R can be scaled down by improving the aspect ratio of our device. We note that this resistance increases to around 1 kR at 77 K and to around 10 kR at 4 K, where the parallel conduction is likely to be frozen out. These results are also consistent with the relatively low carrier density and mobility from an inverted heterojunction. Experience with microwave highelectron mobility transistors that use a ZDEG suggest that we could achieve a base resistance of less than 300R per square, which is sufficient to achieve F , and F , in excess of 100GHz where an identical geometry to the present one, but with the horizontal feature sizes in Fig. IC scaled down by a factor of 100 is used. One might even anticipate some of the advantages seen in the heterojunction bipolar transistor from such scaling down.“ The precision required to expose the base and achieve a shallow ohmic contact is nontrivial. We have found our large area devices prone to early failure from shorting to the collector layer if we subject them to strong biasing. This problem may also be eased with small area devices. As a first step, the results presented here prove the validity of the ZDEG base hot electron transistor.