Abstract
We show that the temperature-dependent resonances measured in the voltage noise of a series of Si δ-doped GaAs/As quantum-well samples originate from fluctuations in the free-carrier concentration of electrons as they are trapped and emitted at deep metastable defects. We identify the main defect observed as the known DX center in III-V semiconductor alloys and present evidence for the existence of previously unreported DX-like traps observed in one of the samples measured in the dark and in the others when continually illuminated with infrared radiation. Further investigation of one of these defects using the Hall effect to measure temperature-dependent changes in free-carrier concentration shows a remarkable peak in the concentration of electrons as a function of temperature when the sample is continuously illuminated. This peak can be understood by using rate equations to describe the dynamics of the possible donor states. In particular, our model indicates a finite ionization energy for the Chadi and Chang -like state for these defects. We propose that the observed phenomena are closely related to the spatial distribution of impurities established during growth. In particular, one might expect a significant probability for the formation of clusters of two or three Si atoms on adjacent group-III sites, which could behave as DX-like states with considerably modified energies. © 1996 The American Physical Society.
- Received 19 January 1996
DOI:https://doi.org/10.1103/PhysRevB.54.2813
©1996 American Physical Society