Carrier extraction from GaSb quantum rings in GaAs solar cells using direct laser excitation

The authors report on the analysis of the hole escape mechanisms from type‐II GaSb quantum rings (QRs) embedded within the active region of a GaAs single junction solar cell. When the solar cell is excited by using a 1064 nm infrared laser with excitation energy lower than the bandgap of the GaAs matrix, photogenerated electron–hole pairs are created directly within the GaSb QRs. The QR photocurrent exhibits a linear dependence on the excitation intensity over several decades. The thermal activation energy was found to be weakly dependent on the incident light level and increased by only a few meV over several orders of excitation intensity. The magnitude of the relative absorption in the author's QRs when directly probed by using a 1064 nm laser with an incident power density of ∼ 2.6 W cm −2 is found to be ∼ 1.4 × 10 −4 per layer. The thermal escape rate of the holes was calculated and found to be ∼ 10 11 to 10 12 s −1 , which is much faster than the radiative recombination rate 10 9 s −1 . This behaviour is promising for concentrator solar cell development and has the potential to increase solar cell efficiency under a strong solar concentration.