Dispersive photoluminescence decay by geminate recombination in amorphous semiconductors

The photoluminescence decay in amorphous semiconductors is described by power law $t^{-delta}$ at long times. The power-law decay of photoluminescence at long times is commonly observed but recent experiments have revealed that the exponent, $delta sim 1.2-1.3$, is smaller than the value 1.5 predicted from a geminate recombination model assuming normal diffusion. Transient currents observed in the time-of-flight experiments are highly dispersive characterized by the disorder parameter $alpha$ smaller than 1. Geminate recombination rate should be influenced by the dispersive transport of charge carriers. In this paper we derive the simple relation, $delta = 1+ alpha/2$. Not only the exponent but also the amplitude of the decay calculated in this study is consistent with measured photoluminescence in a-Si:H.Comment: 18pages. Submitted for the publication in Phys. Rev.

ISOTHERMAL CAPACITANCE TRANSIENT SPECTROSCOPY : ITS APPLICATION TO THE STUDY OF GAP STATES OF a-Si:H

A basic idea of ICTS (Isothermal Capacitance Transient Spectroscopy) for a system of continuously-distributed gap state and experimental data by the ICTS applied to P-doped a-Si:H Schottky barrier diode are presented. It is shown that the ICTS is a useful tool for the study of gap state of a-Si:H whose material parameters are strongly temperature-dependent

ANNEALING STUDIES ON LOW OPTICAL ABSORPTION OF GD a-Si:H USING PHOTOACOUSTIC SPECTROSCOPY

We have performed photoacoustic spectroscopy (PAS), ESR and ir absorption measurements on undoped GD a-Si:H film before and after isochronal annealings, from which absorption coefficient (down to α = 1 cm-1), spin density (Ns) and bonded H content (CH) were determined. It has been found out that the extraporated spectrum of spin-free a-Si:H shows a long exponential tail, and that additional broad absorption is strongly correlated with Ns. The origin of α below Eo is discussed