Spin injection into heavily-doped n-GaN via Schottky barrier

Spin injection and detection in bulk GaN were investigated by performing magnetotransport measurements at low temperatures.A non-local four-terminal lateral spin valve device was fabricated with Co/GaN Schottky contacts.The spin injection efficiency of 21%was achieved at 1.7 K.It was confirmed that the thin Schottky barrier formed between the heavily ndoped GaN and Co was conducive to the direct spin tunneling,by reducing the spin scattering relaxation through the interface states.

Storage and transfer of optical excitation energy in GaInP epilayer:Photoluminescence signatures

GaInP alloy could be the most trusted key material for fabricating super-high-efficiency single-and multijunction solar cells, especially for space applications. The storage and transfer of optical excitation energy in this key alloy is thus a key subject of the energy conversion from optical to electrical. In this article we present a study of the subject through investigating photoluminescence(PL) degradation in the GaInP epilayer at 4 K under the continuous optical excitations of ultraviolet(UV) 325 nm, visible 488.0 and 514.5 nm lasers. It is found that the decline of PL intensity with the irradiation time may be represented by I(t)/I0=(1 + tτ-1)-1+C, where I0 is the luminescence intensity at the beginning of irradiation, a time constant, and C a background. Moreover, the PL degradation degree reduces with increasing the excitation wavelength. In addition, some red shift of the PL peak is observed accompanying with the intensity decline under the UV laser excitation. These PL signatures indicate that the localized carriers within the local atomic ordering domains play a major role in the storage and transfer of the excitation energy via photon recycling processes.

Influence of temperature and reverse bias on photocurrent spectrum and supra-bandgap spectral response of monolithic GalnP/GaAs double-junction solar cell

In this paper, influence of temperature and reverse bias on photocurrent spectrum and spectral response of a monolithic GalnP/GaAs double-junction solar cell was investigated in detail. Two sharp spectral response offsets, corresponding to the bandedge photo absorption of the bottom GaAs and the top GalnP subcells, respectively, show the starting response points of individual subcells. More interestingly, the cell photocurrent was found to enhance significantly with increasing the temperature. In addition, the cell photocurrent also increases obviously as the reverse bias voltage increases. The integrated photocurrent intensity of the top GalnP subcell was particularly addressed. A theoretical model was proposed to simulate the reverse bias dependence of the integrated photocurrent of the GalnP subceU at different temperatures.