Nallathambi Chandrasekaran

GaAs film on Si substrate transplanted from GaAs/Ge structure by direct bonding

A process to transplant GaAs film from a Ge substrate to Si substrate using a direct bonding method is proposed. The scanning electron microscopy picture shows that the GaAs film is uniformly transplanted from Ge to Si. The high-resolution transmission electron microscopy image shows that GaAs is connected to Si by the covalent bonds. The stress of the bonded GaAs on Si is compared with GaAs/GaAs and heteroepitaxially grown GaAs/Ge(before bonding) by a 4.2 K photoluminescence method. The difference in the residual stress between the bonded GaAs/Si sample and GaAs/Si grown by two-step growth is explained by a thermal stress relaxation mechanism during the cooling process.

High-Radiation Resistance of GaAs Solar Cell on Si Substrate Following 1 MeV Electron Irradiation

The current-voltage characteristics of GaAs solar cells grown on GaAs and Si substrates after 1 MeV electron irradiation are compared under darkness and light illumination. It is found that the radiation resistance of the GaAs solar cell on the Si substrate is higher than that on the GaAs substrate. The high radiation tolerance of the GaAs solar cell on the Si substrate is due to the slow generation rate of arsenic vacancies compared with those of the GaAs solar cell on the GaAs substrate caused by electron irradiation.

Effects of Homoepitaxial GaAs/GaAs and Heteroepitaxial GaAs/Si Solar Cells after 1 MeV Electron Irradiation for Space Application

The high-energy electron irradiation effect of GaAs solar cells on Si substrate has been described and the results were compared with GaAs solar cell on GaAs substrates. The solar cells were irradiated with 1 MeV electron in the range of fluences from 1 ×1013 cm-2 to 1 ×1016 cm-2. The solar cell parameters such as short-circuit current (Isc), open circuit-voltage (Voc) and conversion efficiency were studied under dark and AM 0 conditions. The degradation rate of Voc and Pmax of GaAs/GaAs solar cell is faster than GaAs/Si solar cell after the fluences higher than 1015 cm-2. The slow degradation of GaAs/Si solar cell has been attributed to slow generation of As vacancy.

Low-energy proton irradiation effects on GaAs/Si solar cell

In this article we describe the radiation effects of low-energy proton (100 keV, fluences of 3 ×1010, 1 ×1011, 1 ×1012 and 3 ×1012 cm-2) on GaAs solar cells on Si substrates (GaAs/Si) and compare the results with GaAs solar cells on GaAs substrates (GaAs/GaAs). Solar cell parameters such as short-circuit current (Isc), open circuit-voltage (Voc) and conversion efficiency are studied under the AM0 condition. In low proton fluences, the degradation rate of Voc for GaAs/Si is lower than that of the GaAs/GaAs solar cell, due to the insensitivity of the saturation current. At higher proton fluences the solar cell properties are equally degraded for both types of cells.

Effects of 1 MeV Electron Irradiation on the Schottky Diode Characteristics of n-GaAs/Si

We have reported the irradiation of high-energy electrons (1 MeV, fluences of 1×1013, 1×1014, 1×1015 and 1×1016 cm-2) on the Schottky diode characteristics of GaAs layers on Si and GaAs substrates grown by metal organic chemical vapor deposition (MOCVD). After the irradiation, barrier height decreases in Schottky diodes on the GaAs substrate but there is no considerable change in diodes on the Si substrate. The new trap level increased after irradiation in GaAs/GaAs compared with that in the case of GaAs/Si. These experimental results suggest that GaAs devices on a Si substrate have a higher radiation resistance than those on a GaAs substrate after 1-MeV electron irradiation.