Photovoltaic vs. Photoconductive Mode in Photodiodes: Key Differences

This article compares photovoltaic mode and photoconductive mode in photodiodes, outlining the differences and their respective applications. It also provides links to further information on photodiode basics, types, advantages, and disadvantages.

Photodiode Overview

Let’s dive into the two primary operating modes of photodiodes.

Photodiode Photovoltaic Mode

In photovoltaic mode, when light strikes the photodiode’s semiconductor material, it excites electrons to higher energy states. This excitation makes the electrons mobile, leaving behind “holes.” The electrons then migrate towards the cathode terminal, and the holes towards the anode. This movement generates a voltage difference between the two terminals, even without external bias.

Even in the absence of visible light, a small current is produced; this is known as the dark current. This mode is also sometimes referred to as zero-bias mode.

Photodiode Photoconductive Mode

In photoconductive mode, incident light on the photodiode creates electron-hole pairs within the semiconductor material. The application of a reverse bias voltage causes these pairs to move in opposite directions, resulting in a small current flow through the photodiode.

A key advantage of photoconductive mode is its faster response time compared to photovoltaic mode. This speed boost stems from a wider depletion layer and reduced capacitance, both consequences of the applied reverse bias. Consequently, this mode is also known as reverse bias mode.

Photovoltaic Mode vs. Photoconductive Mode: A Comparison

Here’s a table summarizing the key differences between the two modes: