Si-δ-doped GaAs (N2D ≊ 1011 cm−2) samples grown by molecular-beam epitaxy are investigated by using photoreflectance spectroscopy. The oscillations observed above the GaAs fundamental band gap are attributed to the Franz–Keldysh effect in the region between the δ-doped layer and the crystal surface. This ascription is confirmed by detailed studies through varying the cap thickness (250–2500 Å), temperature (10–450 K), and laser pump power (0.05–7 mW/cm2). The surface potential deduced from the Franz–Keldysh oscillations is found to be temperature and laser pump power dependent, which is explained by taking the surface photovoltaic effect into account. The surface Fermi level has been measured by this method and is found to have the value 0.73±0.02 V.
The photoluminescence (PL) of double-barrier resonant tunneling structures (DBRTSs) with undoped electrodes under bias has been studied. The strong band bending across the cathode causes the quantum size effect in the accumulation layer. The resonant tunneling of electrons from the first excited quantum level in the accumulation layer produces a kink in the current-voltage characteristic. It is found that the PL intensity from the quantum well (QW) as a function of bias sharply peaks at the voltage corresponding to the kink. This provides evidence of the interaction between the first excited quantum state in the accumulation layer and the resonant state in the QW.
Growth of high quality GaAs layers directly on Si substrate by molecularbeam epitaxy J. Vac. Sci. Technol. B 5, 815 (1987); 10.1116/1.583759Molecularbeamepitaxial growth and selected properties of GaAs layers and GaAs/(Al,Ga)As superlattices with the (211) orientation
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