<title>Strain-compensated InGaAs/AlGaAsP quantum well intersubband photodetectors for mid-IR wavelengths</title>

Abstract

Quantum well intersubband photodetectors (QWIPs) are potentially important devices for mid- and long-IR wavelengths, especially for focal plane arrays and two-color applications. State-of-the-art QWIPs for detecting light in the mid-IR wavelength range consist of multiple InGaAs quantum wells separated by AlGaAs barriers. The multiple strained InGaAs wells necessary for detection in this wavelength range inevitably lead to lattice relaxation in the epitaxial structure. We have previously demonstrated that the dark current of InGaAs/GaAs QWIPs for detection near 14 microns could be reduced significantly by using strain-compensation to reduce the lattice relaxation in the structure. Here we apply strain-compensation to reduce the relaxation of InGaAs/AlGaAs QWIPs designed for mid- wavelength IR response. We demonstrate the growth of 20 periods of 30A In<SUB>0.35</SUB>Ga<SUB>0.65</SUB>As quantum wells separated by 330A barriers which shows no lattice relaxation as measured by asymmetric x-ray diffraction rocking curves. A strain-compensated QWIP with peak response near 5.5 microns is demonstrated with responsivity of 0.07A/W and 105K background limited operation at 5V bias.