We have investigated a particular class of photovoltaic quantum well intersubband photodetectors. Each period of the active region in these structures consists of four zones, namely an excitation zone, a drift zone, a capture zone, and a tunneling zone. The devices show pronounced photovoltaic behavior and high detectivities. In particular, the responsivity without external bias is substantially enhanced if resonant carrier capture is achieved due to an appropriate design of the capture zone

No abstract

No abstract

We report on a GaAs/AlxGa1−xAs quantum well intersubband photodetector for the long wavelength infrared region, which operates at zero bias voltage. Detection without bias is achieved by using an asymmetrical barrier structure as well as modulation doping, giving rise to a built-in field across the barrier layers. The maximum of the spectral response is centered at 10 μm with a spectral bandwidth of 1.6 μm and a 77 K peak detectivity of 2.5×109 cm√Hz/W at 0 V.

We report on the intensity dependence of the responsivity in quantum well infrared photodetectors (QWIP). A strong reduction of the responsivity is observed already at small excitation powers for a QWIP with N=4 periods. This nonlinearity is caused by a partial screening of the electric field across the main part of the active region. The intensity dependence is analyzed using a phenomenological approach, which allows us to calculate the nonlinearity from the measured dark current and responsivity. Applying this approach to a background-limited 50 period QWIP, we find that the nonlinearity is already present below 1 mW cm(-2) which is less than the thermal background