Cold to hot electron transition devices

A MBE grown negative differential resistance transistor using n+-i-p+-i-n+ structure are presented. Owing to cold to hot electron transition mechanism. Negative differential resistance (NDR) phenomena are well known for the potential applications in high frequency operations. A new class of devices employing resonant tunneling in double-barrier structures have been developed. However, low temperature, low power operation and small peak-to-valley current ratios limit the practical operation for such resonant tunneling devices. The structure incorporated into three-terminal configurations acquires qualitatively new NDR features. Recently, a novel GaAs voltage-controlled bipolar-unipolar transition (BUNDR) prepared by molecular beam epitaxy (MBE) has been proposed. Peak-to-valley current ratios up to 98 at VBE = 5V operated at room temperature have been obtained. The device also has the potential for high power application due to the very large dynamic NDR region as compared to the other devices. In this paper, a simple GaAs homojunction structure with a large dynamic NDR range is proposed and realized. The base region of this structure is formed by inserting a heavily doped thin δp+ layer prepared by molecular beam epitaxy in between tow thicker undoped layers (p-type) with the background concentration about 1014 cm-3. A voltage-controlled N-shaped NDR characteristic was observed in the n+-i-δ-p+-i-n+ structure. The peak-to-valley current ratios can be modulated by changing the applied base-to-emitter bias. The operational mechanisms of these bipolar-unipolar transitions are quite different from those reported earlier