engleski

Study of Cu doped semi-insulating GaAs

Copper, a common contaminant in semiconductors, was deposited onto unheated semi-insulating (SI) GaAs substrates by high vacuum e-beam method. SI GaAs:Cu, as well as referent undoped SI GaAs were annealed in the same manner, at various temperatures (Ta) in 300-800 K range. Cu diffused into SI GaAs and after each annealing step Thermally Stimulated Current (TSC), dark current (Idark) and photocurrent (Ipc) as well as its temperature dependence were measured and compared. At low annealing temperatures, in GaAs:Cu some TSC peaks, denoted by T1, T4a, T5 and T7, exceeded respective peaks from undoped SL GaAs for approximately 50%, while all other TSC peaks remained unchanged. In both materials at low Ta Idark was governed by the EL2 level, situated 0.75 +/- 0.02 eV below conduction band. For higher Ta in Cu doped sample TSC peaks gradually become dominated by Idark, which got governed by a relatively shallow level with activation energy of 0.15 eV. For annealing temperatures up to 720 K, Ipc (T) was very similar for doped and undoped samples. At higher Ta's, however, in SI GaAs:Cu Ipc decreased for more than four orders of magnitude, with characteristic fast quenching at 90 K. For even higher temperatures, SI GaAs:Cu became conductive. We concluded that Cu influenced some defects in SI GaAs and probably participates in their constitution.

GaAs; impurities; defects

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