Novel Grating Coupled and Normal Incidence III-V Quantum well Infrared Photodetectors with Background Limited Performance at 77 K

Abstract

We report four novel III-V quantum well infrared photodetectors (QWIPs) fabricated on the MBE grown n-type GaAs/AlGaAs, AlAs/AlGaAs, and p-type strained layer (PSL) InGaAs/InAlAs material systems. The detection schemes for these QWIPs are based on bound-to-continuum (BTC) and bound-to-miniband (BTM) intersubband transitions with wavelengths covering from 2–6 μm and 8 –14 μm. QWIP-A is a dual mode (PV & PC) operation GaAs/AlGaAs BTC QWIP with heavily-doped enlarged (11 nm) GaAs quantum wells and thick AlGaAs barrier layers (87.5 nm) grown on the semi-insulating (SI) GaAs substrate for 7.7 and 12 μm two-color detection. QWIP-B is a GaAs/AlGaAs BTM QWIP using an enlarged GaAs quantum well (8.8 nm) and a short-period GaAs/AlGaAs superlattice barrier layer grown on (100) SI GaAs. QWIP-C is a normal incidence type-II AlAs/AlGaAs QWIP grown on the (110) SI GaAs for 2 -14 μm multicolor detection. QWIP-D is a normal incidence p-type strained layer (PSL) InGaAs/InAlAs QWIP grown on the (100) SI InP. For QWIP-A and B, a planar square mesh metal grating coupler is used to achieve high coupling efficiency under normal incidence illumination. Detectivities ranging from 109 to 1012 cm-Hz1/2/W have been obtained for these QWIPs at 77 K operation. The PSL-InGaAs/InAlAs QWIP shows the best overall performance, featuring the lowest dark current density ever reported for the QWIPs and a background limited performance (BLIP) at λp = 8.1 μm and T = 77 K.