Photovoltaic Intersubband Photodetectors Using GaAs Quantum Wells Confined by AlAs Tunnel Barriers

Abstract

Intersubband excitation of carriers in quantum well structures has been used extensively in order to realize infrared photodetector devices at 8-12 μm^1--3 and, more recently, novel infrared imaging cameras:^4,5 There has also been an increasing interest in intersubband photodetection in the 3-5 μm regime, first realized in the In_0.53Ga_0.47Asfin_o.52A1_0.48As system⁶. In the case of GaAs MQW structures, this wavelength range is only accessible for indirect-gap Al_xGa_1-x As barrier material, i. e., x > 0.45.^1,7 We have recently realized a different approach where large intersubband spacings are achieved by using double barrier quantum wells (DBQW), i. e., by introducing thin AlAs tunnel barriers between the GaAs wells and the direct-gap Al_rGa_1-x As layers.⁸ Good detector performance was achieved since the lowest conduction subband is strictly confined by the Al_xGa_1-x As layers while the tunneling escape time of the electrons out of the second subband of the quantum well is controlled by the thickness of the AlAs tunnel barriers.