Dark Lift

Introduction

Shining a laser on a p-n junction or any device based upon semiconductor doping causes generation of electron-hole pairs. These electron-hole pairs significantly affect the minority carrier concentration, hence the Fermi energy level and the width of the depletion region. See Figure 1 and Figure 2.

Figure 1: Band structure change with light

The width of the depletion region is

where e is the permittivity, V0 the contact potential, q the electric charge and Na and Nd the concentration of acceptors (p-type) and donors (n-type). The open circuit potential, Voc, is

where gop is the optical yield of electron-hole pairs and gth is the thermal yield of electron-hole pairs. The voltage when light is applied is

Figure 2: p-n junction width as a function of optical carrier concentration

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• Dark Lift Use
• Dark Lift Examples

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