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

Szmulowicz F., Brown G. J., Liu H. C., Shen A., Wasilewski Z. R., Buchanan M.

Opto-Electronics Review

2001

Vol. 9, No. 2

164-172

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.

III-Nitride wide bandgap semiconductors : a survey of the current status and future trends of the material and device technology

Kung P., Razeghi M.

Opto-Electronics Review

2000

Vol. 8, No. 3

201-239

During the past decade, group III-Nitride wide bandgap semiconductors have become the focus of extremely intensive reearch because of their exceptional physical properties and their high potential for use in countless numbers of applications. Nearly all aspects have been investigated, from the fundamental physical understanding of these materials to the development of the fabrication technology and demonstration of commercial devices. The purpose of this paper is to review the physical properties of III-Nitrides, their areas of application, the current status of the material technology (AlN, AlGaN, GaN, GaInN) including synthesis and processing. The state-of-the-art of III-Nitride material quality, as well as the devices which have been demonstrated, including electronic devices, AlxGa₁-xN ultraviolet photoconductors, ultraviolet photodiodes, visible light emitting diodes (LEDs) and ultraviolet - blue laser diodes, will also be presented.