Carrier Lifetime: Free Carrier Absorption, Photoconductivity, and Photoluminescence

Abstract

AbstractIn this article we present a survey of three basic methods of carrier lifetime determination in semiconductor materials. Different methodical approaches are, however, sensitive to different experimental conditions, such as injection level, temperature, surface condition, and to specific physical parameters of defects. This leads to a determination of qualitatively different lifetimes at variable measurement conditions. We concentrate, first, on the interplay of standard competing recombination processes: the Shockley–Read–Hall (SRH) recombination mechanism, the radiative recombination, and the three‐particle Auger recombination. Aspects related to carrier trapping and to carrier diffusion‐associated surface/interface recombination and typical actions to control this problem are considered.A short overview of carrier lifetime extraction from different optical and diffusion length‐based methods as well as from device‐related techniques is presented. Three conceptually different approaches are reviewed such as the quasi‐steady‐state, the harmonic modulated‐type and the dynamic‐type methods and their advantages/disadvantages in terms of the lifetime data interpretation is discussed.In the following sections, three dynamic methods are presented and compared: Free carrier absorption (FCA), photoconductivity (PC), and photoluminescence (PL). The principle of FCA under collinear and orthogonal geometry of the pump and probe beam is explained. Carrier lifetime results in the bulk and scanning techniques such as depth‐profiling and mapping are described. The provided examples cover Si, epitaxial SiC, and GaN materials. The section of PC dynamics presents the main principles of classical lifetime measurements via electrical contacts as well as through noncontact microwave and radio frequency PC detection circuits. Some practical considerations are given. In the PL section, a diversity of carrier lifetime dynamic extraction from the bulk of semiconductors, as well as from semiconductor nanostructures and quantum dots are summarized. At the end, a selection guide for different methods is given by appropriate tables.