Improvement of strained InGaN solar cell performance with a heavily doped n⁺‐GaN substrate

Abstract

We simulated III-V nitride heterojunction solar cells with a Mg-doped GaN/intrinsic InGaN/Si-doped GaN structure. We investigated the threshold dislocation density, the carrier lifetime, and the strain in the InGaN active layer. The conversion efficiency was sensitive to carrier lifetime limited by Shockely-Read recombination rather than the dislocation density. The electric field induced by the piezoelectric effect in the InGaN layer on þc polarity GaN was opposite to that in the depletion region. The recombination of photo-generated carriers in the p-GaN/i-InGaN/ n-GaN solar cell structure took place dominantly at the i/n interface even at 0 V, and the performance was remarkably degraded. It was found that this negative influence of the piezoelectric effect was reduced by a heavy doping of more than 3 Â 10 19 cm À3 into the n þ -GaN layer at the interface.

Investigation of the p-GaN layer thickness of InGaN-based photoelectrodes for photoelectrochemical hydrogen generation

“…We assumed that the residual donor concentrations in InGaN were 1 × 10 17 cm −3 . 21) Structure A can pull the potential in the p-GaN/uid-InGaN interface upward. It is expected that the excited carriers enhance the charge transport.…”

“…In both structures, the highly n-doped linearly graded In x Ga 1-x N (x = 0-0.065) layer pulls down the potential in the InGaN/n-layer interface by screening the polarization charge. 20,21) In comparison with structure A, structure B of the InGaN-based photoelectrode does not contain the uid-and p-GaN layers. After growth of the photoelectrode structures, the p-layer was activated by annealing.…”

“…According to several reports, a high doping concentration in the n-layer can screen the internal electric field, pulling down the potential between the n-layer/absorption layer interface. 20,21) These techniques lead to inhibition of carrier recombination in the photoabsorption layer. Such band engineering is an important factor for improving device performance.…”

“…Figure2shows the schematic band diagrams for the equilibrium state. We assumed that the residual donor concentrations in InGaN were 1 × 10 17 cm −3 21). Structure A can pull the potential in the p-GaN/uid-InGaN interface upward.…”

Large-area III-nitride double-heterojunction solar cells with record-high in-content InGaN absorbing layers

“…The charge of the ionized dopants at the hetero-interfaces is expected to impede the polarization-induced field for high dopant concentrations [9].…”