Thermal Annealing Recovery of Intersubband Transition in Proton-Irradiated GaAs/Al 0.3 Ga 0.7 As Multiple Quantum Wells
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'Air Force Research Laboratory (AFRL/VSSS), 3550 Aberdeen Ave., SE, Kirtland AFB, NM 87117-5776, gingrichaplk.af.mil 2 Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, NM 87131 3 Department of Physics, University of Arkansas, Fayetteville, AR 4 Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, Australian National University, Canberra, AUSTRALIA
ABSTRACT Optical absorption spectra of intersubband transitions in heavily proton irradiated ntype GaAs/AlGaAs multiple quantum wells were studied as a function of isochronal and isothermal annealing. The absorption spectra of intersubband transitions were depleted 4 2 in samples irradiated with 1 MeV proton doses higher than 1.0xl0 cm- . Thermal annealing of the irradiated samples show that the intersubband transitions are recovered. The relatively lower annealing temperatures at which the recovery is observed indicate that the irradiation-induced defects that trapped the two-dimensional electron gas in the quantum wells are vacancy and interstitial related defects. Once these traps are thermally annealed the electrons are released back to the quantum wells, resulting in the recovery of the intersubband transitions.
INTRODUCTION Intersubband transitions in III-V quantum well materials form the basis of a new generation of long and very long wavelength infrared detectors [1,2]. The desire to use these detectors in space has created an interest in the survivability of these materials in space and other high radiation environments. Charge ionization and atomic displacement are the most important effects in irradiated semiconductor materials. Charge ionization has a major effect on device performance since irradiation-induced charge accumulation negatively affects the performance of electronic and optoelectronic devices. Irradiation-induced atomic displacement affects both materials and devices, the effect increasing with increasing dose. A number of studies have been made of the effects of radiation on III-V materials and devices. Some have concentrated on the effects of damage to semiconductor lasers [3], while others have used proton bombardment to shift the laser's operating wavelength [4]. Many studies have used silicon or heavier ions to look at the process of amorphization in bulk materials [5] and in heterostructures [6,7]; studies which investigate proton bombardment of detector structures are much less common [8,9].
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Mat. Res. Soc. Symp. Proc. Vol. 607 © 2000 Materials Research Society
Some investigation of the effects of annealing on damaged material has been made, mostly using high temperature rapid thermal annealing [4,9]. Many operating devices would be damaged by the high temperatures used in such processes, so there is interest in lower-temperature annealing techniques. In this paper we report the results of our initial investigations into the effects of lower temperature annealing on infrared detector structures.
EXPERIMENT The GaAs/A1GaAs structures used in t
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