Dd. Carey et al., INVESTIGATION OF DEEP METASTABLE TRAPS IN SI DELTA-DOPED GAAS AL0.33GA0.67AS QUANTUM-WELL SAMPLES USING NOISE SPECTROSCOPY/, Physical review. B, Condensed matter, 54(4), 1996, pp. 2813-2821
We show that the temperature-dependent resonances measured in the volt
age noise of a series of Si delta-doped GaAs/Al0.33Ga0.67As quantum-we
ll samples originate from fluctuations in the free-carrier concentrati
on of electrons as they are trapped and emitted at deep metastable def
ects. We identify the main defect observed as the known DX center in I
II-V semiconductor alloys and present evidence for the existence of pr
eviously unreported DX-like traps observed in one of the samples measu
red in the dark and in the others when continually illuminated with in
frared radiation. Further investigation of one of these defects using
the Hall effect to measure temperature-dependent changes in free-carri
er concentration shows a remarkable peak in the concentration of elect
rons as a function of temperature when the sample is continuously illu
minated. This peak can be understood by using rate equations to descri
be the dynamics of the possible donor states. In particular, our model
indicates a finite ionization energy for the Chadi and Chang DX(0)-li
ke 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 probabil
ity for the formation of clusters of two or three Si atoms on adjacent
group-III sites, which could behave as DX-like states with considerab
ly modified energies.