Heterojunction wavelength-tailorable far-infrared photodetectors with response out to 70 μm

Abstract

Results are presented on the performance of a heterojunction interfacial workfunction internal photoemission (HEIWIP) wavelength-tailorable detector. The detection mechanism is based on free-carrier absorption in the heavily doped emitter regions and internal emission across a workfunction barrier caused by the band gap offset at the heterojunction. The HEIWIP detectors have the high responsivity of free-carrier absorption detectors and the low dark current of quantum well infrared photodector type detectors. For a 70±2 cutoff wavelength detector, a responsivity of 11 A/W and a D*=1×1013 cmHz/W with a photocurrent efficiency of 24% was observed at 20 μm. From the 300 K background photocurrent, the background limited performance (BLIP) temperature for this HEIWIP detector was estimated to be 15 K. This HEIWIP detector provides an exciting approach to far-infrared detection.

Mid-infrared detection in p-GaAs/AlGaAs heterostructures with a current blocking barrier

“…This leads to achieving a significant improvement in the specific detectivity (D*). Moreover, the mature growth and established processing technology have made p-GaAs/ Al x Ga 1-x As materials systems increasingly attractive for heterojunction interfacial workfunction IR photodetectors (HEIWIP), 12 which operate up to room temperature. 13 In addition, by replacing the constant Al x Ga 1-x As barrier with a graded barrier, achieved by varying the Al mole fraction (x), the detector was found capable of operation in photovoltaic mode.…”

Resonant cavity enhancement in heterojunction GaAs/AlGaAs terahertz detectors

“…1 Recently, a modification using a heterojunction to obtain the work function instead of band gap narrowing was suggested giving the heterojunction interfacial workfunction internal photoemission ͑HEIWIP͒ infrared photodetector. 2 HEIWIP's have the advantage of allowing reduced doping which can lead to lower dark current and improvement in the quality of material. The detection mechanism of the HEIWIP detector involves absorption in the doped emitter layers of GaAs, mainly by free carriers, followed by the internal photoemission of photoexcited carriers across the work function at the Al x Ga 1Ϫx As barrier followed by collection.…”

Effect of a current blocking barrier on a 2–6 μm p-GaAs/AlGaAs heterojunction infrared detector

“…12 Furthermore, dark current suppressing structures were also demonstrated, such as conduction band barriers in nBn photodetectors 13,14 and XBn barrier photodetectors. 15 In general, the main goal in these architectures is to lower the dark current, but with a relatively small compromise to the photocurrent, thus achieving a significant improvement in the specific detectivity (D*).Due to the mature growth and established processing technology of p-GaAs/Al x Ga 1Àx As, these materials systems have become increasingly attractive for demonstrating heterojunction interfacial workfunction IR photodetectors (HEIWIP), 16 which operate up to room temperature. 17 Furthermore, replacing the constant Al x Ga 1Àx As barrier with a graded barrier, achieved by tuning the Al mole fraction (x), was found to enable photovoltaic operation as well.…”

“…Due to the mature growth and established processing technology of p-GaAs/Al x Ga 1Àx As, these materials systems have become increasingly attractive for demonstrating heterojunction interfacial workfunction IR photodetectors (HEIWIP), 16 which operate up to room temperature. 17 Furthermore, replacing the constant Al x Ga 1Àx As barrier with a graded barrier, achieved by tuning the Al mole fraction (x), was found to enable photovoltaic operation as well.…”

“…The valence band offset between the p-GaAs emitter and the undoped Al x Ga 1Àx As barrier forms a heterojunction, which leads to an interfacial work function, 16 controlled by the mole fraction, x, in the Al x Ga 1Àx As barrier. The energy difference between the Fermi level and the top of the barrier is the minimum energy required for internal photoemission, denoted as the activation energy (D).…”