Dark currents in compositionally-graded InxGa1-x As (.53<x<.82)

Best results with light detection in the near-infrared spectrum (0.5-2.5 μm) have been obtained with indium gallium arsenide (In_xGa_1-xAs). One- and two-dimensional arrays of this material are used in applications as diverse as blood glucose monitoring and artwork analysis. In_0.53Ga_0.47As cameras are particularly well suited for night vision using the afterglow of the night sky, especially on moonless nights. This composition is “lattice-matched” to InP substrates and produces dark currents nearly as low as theoretical predictions. However, to detect light in the 2 μm region, it has been necessary to “compositionally-grade” this material to higher indium content and thereby introduce dislocations which can increase dark currents by several orders of magnitude. This paper reviews the current state-of-the-art of compositionally-graded InGaAs, including crystal growth techniques (VPE, OMVPE and MBE), figures of merit, and future projections for this material over the next several years