Test Method for Determining Net Carrier Density Profiles in Silicon Wafers by Capacitance-Voltage Measurements With a Mercury Probe

ABSTRACTWe propose an implementation of the PCD technique to minority carrier effective lifetime assessment in crystalline silicon at 77K. We focus here on (n)-type, FZ, polished wafers passivated by a-Si:H deposited by PECVD at 200°C. The samples were immersed into liquid N2 contained in a beaker placed on a Sinton lifetime tester. Prior to be converted into lifetimes, data were corrected for the height shift induced by the beaker. One issue lied in obtaining the sum of carrier mobilities at 77K. From dark conductance measurements performed on the lifetime tester, we extracted an electron mobility of 1.1x104 cm².V-1.s-1 at 77K, the doping density being independently calculated in order to account for the freezing effect of dopants. This way, we could obtain lifetime curves with respect to the carrier density. Effective lifetimes obtained at 77K proved to be significantly lower than at RT and not to depend upon the doping of the a-Si:H layers. We were also able to experimentally verify the expected rise in the implied Voc, which, on symmetrically passivated wafers, went up from 0.72V at RT to 1.04V at 77K under 1 sun equivalent illumination.

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Interaction Between EL5 and EL6 in Bulk GaAs

MRS Proceedings ◽

10.1557/proc-378-935 ◽

1995 ◽

Vol 378 ◽

Cited By ~ 2

Author(s):

Hiroyuki Shiraki ◽

Yutaka Tokuda ◽

Koichi Sassa

Keyword(s):

Pulse Duration ◽

Carrier Density ◽

Initial Value ◽

Bulk Gaas ◽

Single Level ◽

Wide Range ◽

Capacitance Voltage ◽

Voltage Transient ◽

Transient Spectroscopy ◽

Electron Occupation

AbstractThe interaction between EL5 and EL6 in the n-type bulk GaAs have been observed by using isothermal constant-capacitance voltage transient spectroscopy (CCVTS). Each CCVTS spectrum of EL5 and EL6 was broader than a theoretical one expected for a single level, and was found to be consistently interpreted by two main trap components. With the increase of the filling pulse duration in a wide range, one component of EL6 decreased to about 50 % of its initial value, while one component of EL5 increased and saturated. This variation in peak heights could be reversed by controlling electron occupation fractions of EL5 and EL6 by application of two adjacent filling pulses. Such interaction between both levels was commonly observed in n-type bulk GaAs independent of carrier density.

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