Excess Carrier Lifetime Measurement of Bulk SiC Wafers and Its Relationship with Structural Defect Distribution

Abstract

Excess carrier lifetime in bulk 2-in. SiC wafers was measured by microwave photoconductivity decay (µ-PCD). The mapping technique was used to obtain the lifetime distribution in the entire wafer. We observed the birefringence image and X-ray topograph of the wafers in order to determine the structural defect distribution, and the net donor concentration distribution was also observed by capacitance–voltage measurements. By comparison of lifetime maps with the structural defect distribution, it was found that relatively long lifetime regions correspond to regions with high-density structural defects. The net donor concentration did not show a clear influence on the carrier lifetimes. We confirmed that surface recombination has a negligible effect on the carrier lifetimes, and therefore the lifetimes obtained from mapping measurements are mainly dominated by carrier recombination behavior in the bulk of the wafers.

Excess carrier lifetime and strain distributions in a 3C-SiC wafer grown on an undulant Si substrate

“…On the basis of excess carrier decay curves obtained from μ‐PCD, we mapped the 1/ e lifetime, which is defined as the time taken by the excess carrier to decay from a peak to 1/ e . The portions with strain field could be observed by a microscope with crossed polarizers, which is frequently used to observe defect distribution in SiC wafers . Although we did not have the microscope with a setup to observe amount of strain and stress as reported in Refs.…”

“…Therefore, distribution in the density of defects may show correspondence with carrier‐lifetime distribution. As reported for other SiC polytypes, carrier‐lifetime measurements are effective for observing non‐uniform electrical properties caused by defects in a SiC wafer . Recently, we studied the carrier‐lifetime distributions in (100) surfaces of a 3C‐SiC wafer using microwave photoconductivity decay (μ‐PCD) with sub‐mm mapping .…”

Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method

“…Among these techniques, µ-PCD is the most widely employed because compared to the other two as it exhibits surface roughness insensitivity (i.e., measurable for any given various surface roughness 8,9,10 ) and high signal sensitivity for excited carriers (i.e., using an optimum microwave component). In general, µ-PCD has been preferred for carrier lifetime measurement in SiC and other semiconductor materials 2,5,6,11,12,13,14,15,16,17,18,19 .…”

Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method

“…) and high signal sensitivity for excited carriers (i.e., using an optimum microwave component). In general, µ-PCD has been preferred for carrier lifetime measurement in SiC and other semiconductor materials 2,5,6,11,12,13,14,15,16,17,18,19 .…”