The investigation of excess carrier lifetimes in amorphous silicon by transient methods

Preparation and properties of heavily doped and strongly compensated Ge films on GaAs

“…The exponential increase in mobility with the temperature is a well known fact for amorphous semiconductors. 5,43,44 This behavior is explained for amorphous semiconductors in terms of free charge carrier trapping by the localized states near the conduction band edge.…”

Photo-excited hot carrier dynamics in hydrogenated amorphous silicon imaged by 4D electron microscopy

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The dynamics of charge carriers in amorphous semiconductors fundamentally differ from those in crystalline semiconductors 1,2 due to the lack of long-range order and the high defect density. Despite intensive technology-driven research interests 3,4 and the existence of well-established experimental techniques, such as photoconductivity time-of-flight [5][6][7][8] and ultrafast optical measurements [9][10][11][12] , many aspects of the dynamics of photo-excited charge carriers in amorphous semiconductors remain poorly understood. Here we demonstrate direct imaging of carrier dynamics in space and time after photo-excitation in hydrogenated amorphous silicon (a-Si:H) by scanning ultrafast electron microscopy (SUEM) 13,14 .We observe an unexpected regime of fast diffusion immediately after photoexcitation along with spontaneous electron-hole separation 15 and charge trapping 1 induced by the atomic disorder.

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Relationship between carrier diffusion lengths and defect density in hydrogenated amorphous silicon

“…V B. Spear and Steemers 19 reported from the TOF charge-collection measurements that the hole lifetimes are longer than the electron lifetime in undoped a-Si:H. In their experiments the measurement condition was close to ''in the dark'' as no bias illumination was applied to the samples. The present results have thus indicated that the relationship between p and n is similar also under illumination.…”