Photovoltaic characterisation of GaAsBi/GaAs multiple quantum well devices

- GaAsBi MQW diodes characterised by dark IV, IQE and illuminated IV.
- All devices exhibit diode IV behaviour, with ideality factors < 2.
- Extended absorption observed in strained GaAsBi compared to strained InGaAs.
- IQE shows improvement of carrier collection of GaAsBi devices at reverse bias.

A series of strained GaAsBi/GaAs multiple quantum well diodes are characterised to assess the potential of GaAsBi for photovoltaic applications. The devices are compared with strained and strain-balanced InGaAs based devices.The dark currents of the GaAsBi based devices are around 20 times higher than those of the InGaAs based devices. The GaAsBi devices that have undergone significant strain relaxation have dark currents that are a further 10-20 times higher.Quantum efficiency measurements show the GaAsBi devices have a lower energy absorption edge and stronger absorption than the strained InGaAs devices. These measurements also indicate incomplete carrier extraction from the GaAsBi based devices at short circuit, despite the devices having a relatively low background doping. This is attributed to hole trapping within the quantum wells, due to the large valence band offset of GaAsBi.