•Effect of electron irradiation on wafer-bonded four-junction solar cell was studied.•An end of life remaining factor of approximately 85% was obtained.•The degradation was mainly due to damage on the InGaAsP and InGaAs subcells.•The results indicate a highly radiation resistant bonding interface.For application in space environments, the effect of 1-MeV electron irradiation on wafer-bonded GaInP/GaAs//InGaAsP/InGaAs four-junction solar cell grown by all solid state molecular beam epitaxy was studied. After exposure to 1-MeV electron irradiation at 1×15 e/cm2, an end of life remaining factor of approximately 85% was obtained. The wafer bonding interface was studied by spectral response and transmission electron microscopy. 1-MeV electron irradiation was conducted on the individual InGaAsP and InGaAs single junction cell, respectively. The degradation of the four-junction cell was mainly due to damage on the InGaAsP and InGaAs subcells rather than the bonding interface.

•The power density of resonant tunneling diode can be enhanced by optimizing emitter spacer layer thickness.•The optimized In0.8Ga0.2As/AlAs RTD possesses the capability to reach 3.1 mW at 300 GHz and 1.8 mW at 600 GHz.•The improved fabrication process based on the previous work can precisely control the mesa area of RTDs.•Optimizing ESL thickness provides an efficient way to balance the cut-off frequency and output power of THz RTD oscillators.We demonstrate both theoretically and experimentally that the power density of resonant tunneling diode (RTD) can be enhanced by optimizing emitter spacer layer thickness, in addition to reducing barrier thickness. Compared to the widely used epitaxial structure with ultrathin emitter spacer layer thickness, appropriate increasing the thickness will increase the voltage drop in accumulation region, leading to larger voltage widths of negative differential resistance region. By measuring J-V characteristics, the specific contact resistivity, and the self-capacitance, we theoretically analyze the maximum output power of the fabricated RTDs. It shows that the optimized In0.8Ga0.2As/AlAs RTD with 20 nm emitter spacer thickness and 5 μm2 mesa area theoretically possesses the capability to reach 3.1 mW at 300 GHz and 1.8 mW at 600 GHz.

•InGaAsP solar cells grown by molecular beam epitaxy is investigated.•A high solar cell performance is obtained at a relatively high growth temperature.•Higher growth temperature leads to longer minority carrier lifetime in InGaAsP.•The influence of growth temperature is attributed to miscibility gap in InGaAsP.•InP is more promising as the back surface field layer compared with InAlAs.We report on the study of InGaAsP solar cells grown by solid-state molecular beam epitaxy (MBE) on InP. The effect of growth temperature on device performance is investigated. Under standard one-sun air-mass 1.5 global (AM1.5) illumination, an efficiency of 18.8% has been obtained for In0.78Ga0.22As0.48P0.52 single-junction solar cells grown at high temperature. Time-resolved photoluminescence (PL) results demonstrate that the In0.78Ga0.22As0.48P0.52 optical quality is greatly improved in the case of a high growth temperature. A longer PL decay time of In0.78Ga0.22As0.48P0.52/InP in contrast to In0.78Ga0.22As0.48P0.52/In0.52Al0.48As indicates that InP is more promising as the back surface field for future solar cell performance improvements.

•Carrier recombination dynamics in InGaAsP grown by molecular beam epitaxy is investigated.•The radiative and nonradiative recombination time constants are calculated.•At room temperature, the nonradiative processes dominate the recombination.•Higher doping density leads to shorter PL decay time.•InGaAsP-based single-junction solar cell with 1 eV bandgap is demonstrated.The carrier recombination dynamics of InGaAsP material with a bandgap energy of 1 eV for quadruple-junction solar cells grown by solid-source molecular beam epitaxy have been investigated by the employment of time-resolved photoluminescence (PL) measurement. For the nominally undoped material, the PL decay time increases with increasing temperature, which indicates that radiative recombination dominates the recombination process. The radiative and the nonradiative recombination time constants were calculated on the basis of the temperature-dependent PL decay time and the integrated PL intensity. With the incorporation of Be (as the p-type dopant) into the material, the PL decay time decreases with increasing temperature, and a double-exponential PL decay curve is observed in the case of the material with a higher doping density. An InGaAsP-based single-junction photovoltaic device with a bandgap of 1 eV was fabricated, and an efficiency of 16.4% was obtained under the AM1.5G solar spectra.(a) The temperature dependence of the PL decay time TL for the nominally undoped InGaAsP Sample A. The inset displays the PL decay curve. (b) The temperature dependence of the PL decay time TL for the Be-doped InGaAsP Sample B (lower doping density). The inset displays the PL decay curve. (c) The temperature dependence of the PL decay time TL for the Be-doped InGaAsP Sample C (higher doping density). The inset displays the PL decay curve. (d) Current density–voltage (J–V) characteristic curves of the InGaAsP solar cell under the AM1.5G solar spectra.

•The effect of rapid thermal annealing on InGaAsP grown by MBE is investigated.•The crystal quality of p-type InGaAsP improves greatly after annealing at 800 °C.•The undoped InGaAsP and n-doped InGaAsP have little change after annealing.•The open voltage of InGaAsP solar cell increases by 11% after annealing.•The improvement of p-type InGaAsP after annealing is attributed to Be diffusion.Rapid thermal annealing (RTA) has been performed on InGaAsP solar cells with the bandgap energy of 1 eV grown by molecular beam epitaxy. With the employment of RTA under an optimized condition, the open voltage was increased from 0.45 to 0.5 V and the photoelectric conversion efficiency was increased from 11.87–13.2%, respectively, which was attributed to the crystal quality improvement of p-type InGaAsP and therefore a reduced recombination current inside depletion region. The integral photoluminescence (PL) intensity of p-type InGaAsP increased to 166 times after annealing at 800 °C and its PL decay time increased by one order of magnitude. While the changes of nominally undoped and n-doped InGaAsP were negligible. The different behaviors of the effect of RTA on InGaAsP of different doping types were attributed to the highly mobile “activator” – beryllium (Be) atom in p-type InGaAsP.

•The doping of solid-state Te is successfully controlled.•Growth and properties of Te-doped AlInP grown by MBE were studied.•Te doped AlInP is applied to the solar cell.•Te doped AlInP as the window layer reduces lateral spreading resistance.Solid-state tellurium (Te) is used as an n-type dopant of AlInP grown by molecular beam epitaxy (MBE). The carrier concentration proportionally increases with increasing Te beam equivalent pressure (BEP) up to a high doping density of 1×1019 cm−3. The incorporation of Te into AlInP results in a mirror-like surface at a moderate doping density due to its surfactant effect, while the surface roughness increased with a further rising of Te doping concentration. Furthermore, for the same In and Al flux ratio, the increase of the Te flux leads to a decreased In-content, but little effect on the alloy׳s disorder is observed. The highly Te-doped AlInP was used in a GaAs solar cell as a window layer. As compared with the solar cell with the Si-doped AlInP window layer, the device with the Te-doped AlInP window layer exhibits the higher efficiency and an extended increase under concentrated solar illumination, due to the benefits of the higher doping density in the Te-doped epilayer.