Analysis of carriers transportation of novel GaAs/AlGaAs quantum well infrared photodetectors

In order to overcome the intrinsic difficulties in conventional GaAs/AlGaAs multi-quantum well infrared photodetectors(QWIPs), such as small photocurrent, big dark current and low response speed, a novel tunneling compensation QWIPs structure is proposed in this paper. Based on static Boltzmann Equation and Equilibrium Equation, considering scattering of the ionized impurity and the optical vibration, the transportation process of carriers have been simulated at low temperature. The device is in anti-bias state when adding bias, each periodic unit's maximum voltage is about 1.5V. Because of big resistance the intrinsic type AlGaAs have large voltage, which is about 1.3V. When electrons transport in the depletion region and the N-type GaAs, the transportation time is less than the electron momentum relaxation time. The scattering mechanisms have not yet occurred, and consequently only the perturbation due to the electric field is observed. Each carrier is shifted the same amount in the direction of the field. Then, only a rigid shift of the initial distribution function, proportional to the elapsed time and to the electric field value, will occur. The velocity of all carriers along the field direction, and in turn the drift velocity, increases linearly with time so that that a high value of the drift velocity can be achieved. The result show that carriers in the novel structure, which transported ballistically through the region of quantum well accelerated by the large build-in electric field, have more higher transportation speed and more longer lifetime relative to the conventional QWIPs structure. Due to empty states of the subband in quantum well region, which was generated by incident infrared light, will be filled by tunneling mechanism, it should be expected that the photocurrent would increase with the numbers of quantum wells step by step in the novel structure, otherwise another characteristic would be expected that the absorb wavelength of the photodetector is tunable by different bias level.