On the role of mobility and saturated velocity in the dynamic operation of p-i-n and metal-semiconductor-metal photodetectors

Abstract

We have employed the temperature dependence of the response of lateral p-i-n and metal-semiconductor-metal photodetectors fabricated with Ga0.47In0.53As active regions to determine the role of low and high-field transport properties of electrons and holes in the speed and frequency response. The p-i-n structures exhibit a response with two characteristic time constants and show a significantly larger improvement in response time at lower temperatures than that expected from improvements in saturated velocities alone. It is suggested that upon excitation by photons, the initial stage of the response is characterized by low-field ambipolar conditions with electron transport and collection dominating the response. This is followed by high-field unipolar conditions where hole transport and collection dominates the response. Thus, low-field mobility, which has a stronger temperature dependence, is also important to the operation of photodetectors.