Toward Ga‐Free Wavelength Extended 2.6 µm InAsP Photodetectors with High Performance

Abstract

Abstract Short‐wavelength infrared (SWIR) photodetectors are of great interest owing to their unique advantages of SWIR imaging such as better penetration ability and improved sensitivity that allow high‐resolution imaging. Commercially, extended In x Ga 1‐ x As heterojunction detectors with cut‐off wavelengths beyond λ c = 1.7 µm are incorporated into SWIR imagers. However, their large dark current and limited cut‐off wavelength tunability prevent their widespread use in SWIR imaging. Herein, a novel InAs 0.85 P 0.15 homojunction detector with λ c = 2.6 µm is achieved through lattice and bandgap engineering with well‐designed InAs y P 1‐ y metamorphic buffers. Compared to conventional In 0.83 Ga 0.17 As/InP detectors with a lattice mismatch of f = 2.0%, the InAs 0.85 P 0.15 detector with f = 2.7% exhibits full strain relaxation and lower surface roughness (2.4 nm due to its superior crystallinity). Photocarrier generation in the InAsP detector is more efficiently supported by a smaller entropy for electron–hole pair formation. The lower trap density and longer carrier lifetime of the InAsP detector decrease the dark current, leading to high uniform detectivities of ≈1.0 × 10 9 cm Hz 1/2 W −1 over a wider voltage range at 300 K. Such an InAsP metamorphic detector with excellent photodetection capabilities is expected to find applications in the implementation of large‐format focal plane arrays for extended SWIR imaging.