Photocurrents in p-n Si diodes under high intensity (pulsed-laser) illumination: Quantum yields and kinetic evaluation

Abstract

The photoelectric response of p-n Si photodiodes under pulsed laser illumination (half width 10 ns) at 532 nm was studied as a function of dose which was varied over 6 orders of magnitude. The photocurrent transients are dominated by a plateau-like feature due to the build up of space charge at the intensities used. Increasing bias voltage increases the height of the plateau and decreases its length. In the low-dose range the length of the transient increases linearly with dose and the collected charge (integrated current) reaches a constant value. At high doses (above 10⁻⁵ J/pulse · cm² or 2.7×10¹³ quanta/pulse · cm²) considerable charge loss (decrease in quantum yields) is accompanied by a less than proportional increase of the transient lifetime. From model calculations the dose and voltage dependence of the quantum yield of charge collection is shown to be the result of competition between current flow and first and higher order recombination. The model calculations are consistent with experimental results. Rate constants have been obtained by fitting.