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

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 In(0.61)Ga(0.39)P/In(0.14)Ga(0.86)As 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 x 10(12) cm(-3) for the In(0.14)Ga(0.86)As and 2 x 10(14) cm(-3) for the In(0.61)Ga(0.39)P sub-detectors, enabling low, room temperature reverse bias (-2 V) dark current densities of 4 x 10(-8) A cm(-2) and 7 x 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 x 10(11) cm Hz(1/2)/W for the In(0.14)Ga(0.86)As sub-detectors (at 980 nm), and 0.30 A/W and 2.0 x 10(14) cm Hz(1/2)/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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3642981]