Dong Hwan Jun

Te doping in the GaAs tunnel junction for GaInP/GaAs tandem solar cells

Heavily tellurium (Te)-doped GaAs layers with diethyltellurium (DETe) grown by metalorganic chemical vapor deposition (MOCVD) were investigated. The existence of Te-rich microprecipitates might degrade both the electrical and optical properties. Compared to Si doping, the tunnel junction diode doped with Te doping revealed lower tunneling resistance. A comparative study using both Si and Te doping in the GaAs tunnel junction of GaInP/GaAs tandem solar cells showed a higher efficiency for Te doping. Therefore, the GaAs tunnel junction with Te doping can be considered to improve the device performance of GaAs-based multi-junction solar cells.

Effects of Thermal Annealing on In Situ Phosphorus-Doped Germanium

In this letter, we investigate the electrical behavior of vacancy <i>V</i>_Ge defects in Ge at various thermal annealing conditions through electrochemical capacitance-voltage analysis. Then, the effects of the annealing process on Ge n⁺/p junction diodes were also studied with <i>J</i>-<i>V</i>, transmission electron microscopy, and secondary ion mass spectroscopy measurements in the aspects of point-defect healing and dopant diffusion/loss phenomena. The <i>V</i>_Ge defects tend to heal by recombining with Ge interstitial atoms as the annealing process temperature increases. However, the diffusion/loss problems of P atoms in Ge become severe at above 500^°C. Therefore, an optimal postfabrication annealing process at 600^°C is proposed in terms of point-defect healing and dopant diffusion/loss reduction.

\hbox{n}^{+}/\hbox{p}

Tellurium (Te) doping of InGaP with diethyl Te (DETe) was investigated to apply for tunnel junctions (TJs) in multijunction solar cells. When the DETe flow rate was 2 sccm, the electron concentration was found to increase with decreasing growth temperature. The obtained electron concentration reached up to ~1 × 1019 cm-3. The photovoltaic (PV) properties of InGaP/InGaAs/Ge triple-junction solar cells with a Te-doped InGaP layer in TJ were measured under concentrated light condition. Here, Te-doped InGaP layers in TJ were prepared using different growth temperatures ranging from 540 °C to 660 °C. Compared with other samples, open-circuit voltage (VOC), fill factor, and conversion efficiency were higher for the sample with an InGaP grown at 570 °C. For this sample, external quantum efficiency was also found to be higher than the other samples, associated with the improved crystalline quality.