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GaAs/AlGaAs p-type multiple-quantum wells for infrared detection at normal incidence: model and experiment

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The Second International Conference on Solid State Crystals '2000 (ICSS'2000) ; (9.10-13.10.2000 ; Zakopane , Poland)
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The development of devices for mid-, long-, and very long-wavelength infrared (IR) detection has benefited greatly from advances in band-gap engineering. Recently, there has been great progress in the development of n-type GaAs/AlGaAs quantum well infrared photoconductor (QWIP) detector arrays in all three technologically important wavelength windows. p-type GaAs/AlGaAs QWIPs represent a viable alternative to n-type GaAs/AlGaAs QWIPs, offering the advantage of normal incidence absorption without the need for grating couplers. The maturity of the MBE of GaAs/AlGaAs layered materials offers the possibility of mass producing low cost, high performance, large size, high uniformity, multicolour, high frequency bandwidth, two-dimensional imagine QWIP arrays. This paper describes progress in optimising the performance of p-type GaAs/AlGaAs QWIP through modelling, growth, and characterisation. Using the 8x8 envelope-function approximation (EFA), a number of structures were designed and their optical absorption calculated for comparision with experiment. Samples were grown by MBE based on the theoretical designs and their photoresponse measured. p-type QWIPs were optimised with respect to the well and barrier widths, alloy concentration, and dopant concentration; resonant cavity devices were also fabricated and temperature dependent photoresponse was measured. The quantum efficiences and the background-limited (BLIP) detectivities under BLIP conditions of our p-QWIPs are comparable to those of n-QWIP; however, the responsivities are smaller. For our mid-IR p-QWIPs, the 2D doping densities of (1-2)x10¹² cm⁻² maximised the BLIP temperature and dark current limited detectivity by operating at around 100 K. At 80 K, the detectivity of the optimum doped sample was 3.5x10¹¹ cmHz¹/²/ W at 10 V bias. Barrier widths greater than 200 A were sufficient to impede the tunneling dark current; resonant cavities enhanced absorption fivefold.
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bwmeta1.element.baztech-article-BWA2-0005-0086
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