Optically-aligned visible/near-infrared dual-band photodetector materials and devices on GaAs using metamorphic epitaxy

Abstract

A monolithic, epitaxially-integrated, vertically-aligned, multi-band photodetector architecture has been demonstrated via the successful growth and fabrication of metamorphic back-to-back n-i-p/p-i-n In0.61Ga0.39P/In0.14Ga0.86As visible/near-IR dual-detector devices. The back-to-back diode design enables simultaneous and independent operation of detectors in both bands with low optical cross talk (<−10 dB outside the 690–720 nm range) and complete electrical isolation between the sub-detectors. The high electronic quality of the resultant metamorphic materials was confirmed via deep level transient spectroscopy, which revealed total trap concentrations of 5 × 1012 cm−3 for the In0.14Ga0.86As and 2 × 1014 cm−3 for the In0.61Ga0.39P sub-detectors, enabling low, room temperature reverse bias (−2 V) dark current densities of 4 × 10−8 A cm−2 and 7 × 10−12 A cm−2, respectively. High responsivity and specific detectivity values, at a working bias of −2 V, were measured: 0.41 A/W and 8.6 × 1011 cm Hz1/2/W for the In0.14Ga0.86As sub-detectors (at 980 nm), and 0.30 A/W and 2.0 × 1014 cm Hz1/2/W for the In0.61Ga0.39P sub-detectors (at 680 nm). The successful integration of high-quality lattice-mismatched materials, combined with the excellent sub-detector performances, demonstrate the potential for extending such a multi-band photodetector technology to achieve simultaneous detection of a wide range of wavelength bands with tunable cut-off wavelengths.