Turkish Journal of Physics




Si-doped single Ga_{0.51}In_{0.49}P layers and GaInP/InGaAs/GaAs modulation doped field-effect transistor structures grown by gas source molecular beam epitaxy were characterized in detail through Hall-Effect and Deep Level Transient Spectroscopy techniques. Electrical characterization of the undoped and moderately Si-doped (N_D = 3 x 10^{17} cm^{-3}) GaInP layers yielded an electron trap with an activation energy of 0.75 eV and a temperature dependent capture cross section with a capture barrier of 0.593 eV showing DX center properties. The trap was not detected in highly Si doped (N_D = 4 x 10^{18} cm^{-3}) as grown layers suggesting that it is a defect complex including a residual impurity. An anomalous decrease in the free carrier concentration of GaInP was observed after the samples were annealed at temperatures typically used in device processing. While other explanations may be possible, this can be attributed to Si atoms moving from donor to acceptor sites. Very high two-dimensional electron gas density (2.6 x 10^{12} cm^{-2} at 30 K) was achieved in the lattice matched (x = 0) structure. The strained structures were found to be very sensitive to heat treatment and another level with dislocation trap characteristics was detected in these structures. Persistent photoconductivity and a significant reduction in the interface sheet electron density were observed in the strained samples after annealing. This can partly be attributed to the strain relaxation at the heterointerface. With no detectable traps in heavily Si-doped GaInP and with very high two dimensional electron gas densities, GaInP/InGaAs/GaAs seems to be a promising material system for modulation doped field-effect transistor applications.

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