Effect of the first barrier thickness on resonance tunnelling in single quantum well infrared photodetectors

Abstract

To understand nature of resonance tunnelling in double barrier/single quantwn well (QW) structures, we have investigated the current generation mechanisms of such structures. Since we were interested only in the resonance current from the emitter contact to the quantwn well the second barrier thickness was made to be large in order to stop the resonance tunnelling from the quantum well to the collector contact.

In this work we have investigated the current-voltage characteristics at 77 K for three structures with emitter barrier thickness 100 A, 150 A, and 200 A of AlO.27Gao73AS,a 40 A thick GaAs QW and 500 A thick AlO.27Gao.73AScollector barrier and the whole structure was sandwiched between two doped (n=IAxl 018 em") GaAs layers.

This work shows that our theoretical model provides a good agreement between the theoretically calculated and measured current-voltage relations for several orders of magnitude in current for the sample with 150 A thick emitter. Therefore we are hopefully presented the theoretically calculated current-voltage relations for the other structures also. The theoretical model consists of resonance current that formulated by the Transfer Hamiltonian technique of resonance tunnelling and non-resonance current from the emitter contact and thermally assisted field emission current from the QW.

Our results show that the total current and the electron accumulation in the QW increase with decreasing emitter thickness. Even though this effect enhances the performance of infrared detectors based on such structures and the parallel increase in the dark current will cause an increase in the noise level.

The authors gratefully acknowledge the supports from the International Science Program in Physical Science, Uppsala, Sweden, The Chalmers University of Technology, Gothenburg, Sweden and the University of Peradeniya.