High-detectivity GaAs quantum well infrared detectors with peak responsivity at 8.2 μm

Abstract

GaAs quantum well infrared detectors with peak responsivity at 8.2 μm and significant response beyond 10 μm have been demonstrated with detectivities of 4×1011 cm (Hz)1/2 /W at 6 K; this detectivity is the highest reported for a quantum well detector. The detectors comprised 50 GaAs quantum wells of width 40 Å with an average Si doping density of 1×1018 cm−3 separated by 280-Å barriers of Al0.28Ga0.72As. In this design, the state to which electrons are excited by infrared absorption and from which they are subsequently collected lies in the continuum above the energy of the Al0.28Ga0.72As conduction-band minimum. The maximum detector responsivity was mesured to be 0.34 A/W. The device dark current density is 5.5×10−6 A/cm2 with the detector biased for maximum detectivity (3.5 V), and the dark current remains constant with increasing temperature up to 50 K. The detector noise current was observed to be a constant fraction (70%) of the shot noise down to noise currents of 10−14 A/(Hz)1/2. A theoretical model for the dark conduction process in a quantum well detector has been developed which successfully predicts the observed dark current noise.

Effects of Rapid Thermal Annealing on the Device Characteristics of Quantum Well Infrared Photodetectors

“…The intersubband absorption coefficient of a multiple-quantum-well or, in general, any periodic or superlattice structure can be derived from Fermi's (4) where e is the magnitude of the electronic charge, n r is the refractive index of the material, c is the freespace speed of light, e 0 is the free-space permittivity, m 0 is the free-space electron mass, and h~o is the energy of a photon. En, q is the energy eigenvalue of a state with wave vector q in the n th subband of a periodic structure, and N n is the volume density of electrons in the state E .…”

Recent Progress in Quantum Well Infrared Photodetectors

“…Rapid progress has recently been made in quantum well infrared photodetectors [1][2][3][4][5][6][7][8][9][10][11][12][13][14] (QWIPs), including extension to both longer 15 (A. = 18 11m) and shorter 16 (A.…”

Noise gain in single quantum well infrared photodetectors

“…1 A great deal of attention has also been paid to the analysis of the current noise, both because the amount of noise sets the lower limit for photon detection of the device and because the noise measurements provide a means for optical gain determination. [2][3][4][5][6][7][8] A photoconductive gain g opt higher than unity with a detectivity D*ϭ1ϫ10 10 cm Hz 1/2 /W at 68 K for a detector cutoff wavelength of c ϭ10.7m, was for the first time found in a GaAs/Al x Ga 1Ϫx As QWIP, based on bound-tocontinuum intersubband transitions, by Hasnain et al 9 QWIP infrared detectors similar to that described in Ref. 9 were later studied by other authors.…”