NUSOD Blog

Connecting Theory and Practice in Optoelectronics

How to simulate the photogating effect in InAs nanowire phototransistors?

phototransistorSemiconductor nanowires promise light detection with enhanced sensitivity and faster transport speed. However, the short photocarrier lifetime, small light-sensing area, and weak optical absorption of nanowires cause serious problems. A possible solution lies in the photogating effect of semiconductor nanostructures, which was recently utilized in graphene-based phototransistors. Photocarriers located near the conductive channel form a strong local electric field to regulate the channel conductance through capacitive coupling.

We have now applied this photogating effect to core/shell-like InAs nanowires resulting in an anomalous photoresponse.[1] A self-assembled ‘photogating layer’ near the nanowire surface traps electrons generated in the core and forms a built-in electric field that modulates the core conductance under optical illumination. In this design, majority carriers, i.e., electrons, are contributing to the photocurrent. The whole channel of the transistor, as the effective photosensitive region, responds to the light signal. The fabricated devices exhibit anomalous high photoconductive gain of -105 and fast response time 12 ms.

Who can help us with the numerical simulation of such anomalous photoresponse based on the photogating effect?

[1] N. Guo et al., Advanced Materials 26, 8203 (2014).

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