OBSERVATION OF ELECTRICALLY RESETTABLE NEGATIVE PERSISTENT PHOTOCONDUCTIVITY IN INAS ALSB SINGLE QUANTUM-WELLS/

The mechanism of the negative persistent photoconductivity (NPPC) in I nAs/AlSb single quantum wells is discussed. The molecular beam epitaxy grown single InAs quantum well sample is made into Hall bars with the substrate as the backgate. Using the newly designed buffer, the gate bias can deplete or enhance the two-dimensional electrons in the InAs quantum well without substantial gate leakage current. Based on the 4. 2 K magnetoresistance data, and the fact that the trapped electrons ca n be redistributed by gate bias, we conclude that: the NPPC effect at low temperatures is a result of the capture of photoexcited electrons by ordinary, deep donors in AlSb. Numerical modeling using physical as sumptions can quantitatively explain our experimental observation, and the calculated AlSb donor energy is 0.41+/-0.05 eV above the AlSb val ence band maximum, with 4 x 10(16)/cm(3) to 10(17)/cm(3) in concentrat ion. The previously discussed DX-center-like characteristic of deep le vels in AlSb, i.e., lattice-relaxation with a relatively high activati on energy, is not evidenced in this work. (C) 1996 American Institute of Physics.