Ming Tan

Investigation of InGaAs thermophotovoltaic cells under blackbody radiation

The efficiency calibration of In GaAs thermophotovoltaic (TPV) cells with band gap energies of 0.6 and 0.74 eV under blackbody radiation is performed on the basis of the combination of measurement with theoretical calculation. Efficiencies of 19.1% for the 0.6 eV InGaAs cell and 16.4% for the 0.74 eV InGaAs cell are obtained at the radiation temperature of 1323 K. The notable differences in reverse saturation current density and ideality factors under the blackbody radiation and standard solar spectrum illumination indicate the significant effect of the radiation spectrum on the detailed understanding of devices

Room-temperature wafer bonded InGaP/GaAs//InGaAsP/InGaAs four-junction solar cell grown by all-solid state molecular beam epitaxy

An InGaP/GaAs tandem cell on a GaAs substrate and an InGaAsP/InGaAs tandem cell on an InP substrate were grown separately by all-solid-state molecular beam epitaxy. A room-temperature direct wafer-bonding technique was used to integrate these subcells into an InGaP/GaAs//InGaAsP/InGaAs wafer-bonded solar cell, which resulted in an abrupt interface with low resistance and high optical transmission. The current-matching design for the base layer thickness of each cell was investigated. The resulting efficiency of the four-junction solar cell was 42.0% at 230 suns, which demonstrates the great potential of the room-temperature wafer-bonding technique to achieve high conversion efficiency for cells with four or more junctions.

Transparent conducting indium-tin-oxide (ITO) film as full front electrode in III–V compound solar cell*

The application of transparent conducting indium-tin-oxide (ITO) film as full front electrode replacing the conventional bus-bar metal electrode in III–V compound GaInP solar cell was proposed. A high-quality, non-rectifying contact between ITO and 10 nm -GaAs contact layer was formed, which is benefiting from a high carrier concentration of the terrilium-doped -GaAs layer, up to 2 . A good device performance of the GaInP solar cell with the ITO electrode was observed. This result indicates a great potential of transparent conducting films in the future fabrication of larger area flexible III–V solar cell.

1-MeV electron irradiation effects on InGaAsP/InGaAs double-junction solar cell and its component subcells

Key Laboratory of Functional Materials and Device for Special Environments, Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011, China; Xinjiang Key Laboratory of Electronic Information Material and Device, Urumqi 830011, China; University of Chinese Academy of Sciences, Beijing 100000, China; Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China

Effect of high temperature rapid thermal annealing on optical properties of InGaAsP grown by molecular beam epitaxy

The effect of rapid thermal annealing (RTA) on the optical properties of InGaAsP with band-gap energy of around 1.05 eV for quadruple-junction solar cells grown by molecular beam epitaxy (MBE) has been investigated. The photoluminescence (PL) spectrum of InGaAsP film annealed at 800 °C has strong integrated intensity and low activation energy of band-tail states. The time-resolved PL measurement shows that the decay time of the InGaAsP annealed at 800 °C and as-grown one are 11.6 ns and 3.0 ns at 10 K, respectively. An S-shape PL decay time as a function of temperature for the InGaAsP annealed at 800 °C is observed and is explained by the carrier relaxation dynamics. The RTA process induces reorganization of In and Ga inside the alloy due to the existence of miscibility gap in InGaAsP grown by MBE owing to the Be diffusion at high temperature and results in an increased composition uniformity and an improved PL intensity.

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace. The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements. The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission, which indicates that Zn was commendably diffused into InP layer as the acceptor. High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 °C for 10 min. Furthermore, more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process. Based on the above Zn-diffusion technique, a 50 μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of −5 V and a high breakdown voltage of larger than 41 V (I < 10 μA). In addition, a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.

Effects of buffer layer and back-surface field on MBE-grown InGaAsP/InGaAs solar cells

Solid-state molecular beam epitaxy (MBE)-grown InGaAsP/InGaAs dual-junction solar cells on InP substrates are reported. An efficiency of 10.6% under 1-sun AM1.5 global light intensity is realized for the dual-junction solar cell, while the efficiencies of 16.4 and 12.3% are reached for the top InGaAsP and bottom InGaAs cells, respectively. The effects of the buffer layer and back-surface field on the performance of solar cells are discussed. High device performance is achieved in the case of a low concentration of oxygen and weak recombination when InGaAs buffers and InP back-surface field layers are used, respectively.