Long-wavelength (0.1-1.6 mu m) In0.53(GaxAl1-x)0.47 As/In0.53Ga0.47As MSM photodiode

Summary form only given. The authors report a novel metal-semiconductor-metal (MSM) Schottky photodiode using a nominally lattice-matched In_0.53(Ga_xAl_1-x) _0.47As (graded)/In_0.53Ga_0.47As structure grown by molecular beam epitaxy on a semi-insulating InP substrate. The approach to barrier enhancement uses a lattice-matched compositionally graded InGaAlAs capping layer. This lattice-matched layer does not suffer from the nonradiative recombination centers which can result from strained/relaxed layers or superlattice interfaces. Abrupt band-edge discontinuities, which inhibit the collection of photogenerated carriers, are also eliminated. A detector responsivity of 0.35 A/W was measured at 1.3 mu m with a 10-V applied bias; the corresponding internal quantum efficiency is in excess of 90%. The associated dark currents are very low: 35 nA at 10 V and 500 nA at 20 V. Detector capacitance was 70 fF. Preliminary high-speed measurements with a gain-switched 1.3- mu m laser diode show an instrumentation-limited impulse response of 55 ps.