ISSN:
1432-0630
Keywords:
72.20.F
;
72.20.J
;
72.40
;
72.80.E
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract The persistent photoconductivity effect in Si-dopedn-Al x Ga1−x As layers grown by molecular beam epitaxy on (100)GaAs substrates has been investigated by detailed Halleffect and capacitance measurements at 10–300 K. In the alloy composition range 0.25〈x 〈0.40 the electrical properties ofn-Al x Ga1−x As are governed by a deep electron trap having an emission barrier of 0.34–0.40 eV (depending on the doping concentration), as determined by admittance measurements. The concentration of deep electron traps, deduced from low-temperature capacitance measurements, is found to coincide with the amount of persistent photoconductivity observed in the material. Consequently, the earlier proposed population of two-dimensional subbands at the Al x Ga1−x As/GaAs-substrate hetero-interface, i.e. charge separation bymacroscopic barriers, can not account for the measured high overall number of persistent photoexcited carriers. Instead, the vanishing small capture rates of photoexcited electrons result frommicroscopic capture barriers. The dominant deep electron trap, which we attribute to deep donor-type (DX) centers, is found to be homogeneously distributed throughout the Al x Ga1−x As layer depth. From our Hall effect measurements a trap depth of 0.05–0.12 eV (depending on the doping concentration) below the conduction band is derived. The capture barrier is thus in the order of 0.30 eV. This value is in excellent agreement with data obtained from liquid phase epitaxially grown Si-dopedn-Al x Ga1−x As.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00617831
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