Optimization of high detectivity infrared hot-electron transistors at low temperature

In this paper, we report a 10 /spl mu/m-cutoff infrared hot-electron transistor (IHET) with extremely high detectivity, D*>7.5/spl times/10/sup 12/ cm/spl radic/Hz/W at 4.2 K. This large D* is accomplished by using InGaAs material in the quantum wells and by using a low filter barrier at the collector for the large photocurrent transfer ratio. We have verified the detector performance by explicitly performing noise characterization at low temperatures. We found that the noise of the quantum well infrared photodetector, which forms the emitter of the IHET, is dominated by 1/f noise and bias-independent noise. The 1/f current noise is due to the conductance fluctuation in impurity-assisted tunneling via DX centers in the quantum well barriers. The filter barrier of the IHET blocks the impurity-assisted tunneling and hence its noise at the collector and thus improves the detector sensitivity.