Bound-exciton effects in the photocurrent spectrum of CdS single crystals

Abstract

The effects of infra‐red quenching, oxygen surface coverage, heat treatment, and additional intrinsic illumination on the spectral dependence of photoconductivity of Class I CdS crystals are presented. Profound changes in the near‐band‐edge photoconductivity when measured near 77 °K were observed. In particular, additional infra‐red caused almost complete quenching in the near‐band‐edge region. Additional intrinsic illumination (4500 Å) caused an enhancement in this region that was over and above the sum of the separate contributions. Oxygen surface coverage was found to cause a quenching of the photoconductivity in this region while having little effect on the intrinsic photoconductivity. Heat treatment restored the photoconductivity. These results are attributed to a modification of the charge character of various centers located in the near‐surface region to which excitons can become bound.

Эффекты ионной бомбардировки в спектрах краевой фотопроводимости и в вольт-амперных характеристиках кристаллов CdS

“…В исходном состоянии (до облучения) в спектре проявляется ТС второго типа [5], где линиям поглощения экситонов, спектральные положения которых обозначены стрелками A, B и C, соответствуют минимумы фототока (кривая 1). С длинноволновой стороны края поглощения, в спектральной области ∼ 492 нм, проявляется слабовыраженный дополнительный максимум фототока " примесной" природы [7,8] (I 1 в обозначениях [9]).…”