Static and dynamic properties of a GaAs p-i-n position-sensitive detector (PSD)

A GaAs-based p-i-n structure which is layer-compatible to a commercial heterojunction bipolar transistor (HBT) was employed to fabricate a visible-light position-sensitive detector (PSD) with a long distance of 14 mm between two coplanar contacts. Sensing properties of the GaAs p-i-n PSD operated in the lateral photovoltaic mode were obtained by using visible-light sources with a power of 1-3 mW. The measured sensitivity was 14.3 ± 0.05 mV/mm, resulting in a sensitivity-distance product of 200 ± 0.5 mV, for the fabricated PSD responding to a 3 mW 638 nm red light. The estimated nonlinearities were as small as 0.9 ± 0.05%-1.9 ± 0.05%, 1.8 ± 0.05%-2.3 ± 0.05%, and 0.3 ± 0.05%-1.3 ± 0.05% for the PSD tested under the 405 nm, 532 nm, and 638 nm lights, respectively. Such a long linear distance is possibly attributed to carrier's large diffusion lengths associated with the GaAs p-i-n layers. Another PSD was fabricated with three-terminal configuration using the same GaAs-based p-i-n structure. Thus, the three-terminal PSD can be operated in both of the lateral and transverse photovoltaic modes. A PSD's differential output from two transverse photovoltaic voltages showed a sensitivity of 11.1 ± 0.05 mV/mm with a 0.3 ± 0.05% nonlinearity. Furthermore, transient responses of the PSD's LPV to the illumination and interdiction of the visible lights were included. Response time of 60 ± 4 μs for the 532 nm green light compared to those of 134 ± 2 and 99 ± 2 μs for the 405 nm blue and 638 nm red lights, respectively, will be investigated to realize the proposed visible-light PSD.