GHz-rate single-photon-sensitive linear-mode APD receivers

Abstract

ABSTRACT We report the design, fabrication, and test of a new InGaAs avalanche photodiode (APD) for short-wavelength infrared (SWIR) sensing applications at 950–1650 nm. The APD is grown by molecular beam epitaxy (MBE) on InP substrates from lattice-matched InGaAs and InAlAs alloys. Avalanche multiplication inside the APD occurs in a series of asymmetric gain stages whose layer ordering acts to enhance the rate of electron-initiated impact-ionization and suppress the rate of hole-initiated ionization when operated at low gain. Measurements have verified much lower excess multiplication noise and much higher avalanche gain than is characteristic of APDs fabricated from the same semiconductor alloys in bulk. At room temperature, multipli cation-enhanced APDs (MAPDs) of this design were found to have excess noise characterized by an effective ionization coefficient ratio of k = 0.02 to a gain of M = 100. The impulse response duration of a 75- m-diameter APD was measured to be less th an 1 ns when operated at a gain of M = 50, with a rise time of 225 ps and a fall time of 550 ps. High-rate single photon counting at 1064 nm was demonstrated with multiple 10-stage APDs operated below their breakdown voltage, using a commercial 2-GHz transimpedance amplifier (TIA) chip. Single photon detection efficiencies as high as 70% were measured for signal photon rates of 50 MHz. Keywords: avalanche photodiode, APD, single photon counting, laser communications, lasercomm, laser radar, LADAR