Joel I. Haberman

An rf bridge technique for contactless measurement of the carrier lifetime in silicon wafers

A contactless rf technique has been developed for measurement of the photoconductivity induced in silicon wafers by a flash of light from GaAs laser diodes. The carrier lifetime inferred from the photoconductivity decay correlates well with diffusion length measurements made on solar cells fabricated from the same wafers. The technique has been applied successfully to silicon whose resistivity is as low as 0.1 Ω cm and lifetime as short as 0.2 μs.

Effects of interfacial charge on the electron affinity, work function, and electrical characteristics of thinly oxidized semiconductor‐insulator‐semiconductor and metal‐insulator‐semiconductor devices

A phenomenological theory involving interfacial charge is presented to account for the result that the diode constant n at low forward biases might be temperature dependent in some thinly oxidized (< 20 A) semiconductor‐insulator‐semiconductor and metal‐insulator‐semiconductor devices, resulting in parallel I‐V curves. Neither multistep tunneling through the semiconductor space‐charge region, nor conventional thermionic emission over the barrier, can explain the low‐voltage portion of the I‐V characteristics. In this paper it is shown that an interfacial charge redistribution occurs with changes in temperature, resulting in changes in the electron affinity of the base semiconductor and in the work function of the contact material. This results in a linear dependence of n on reciprocal temperature. An explanation is presented to account for the large temperature coefficient that has been observed for both the diffusion potential VD and open‐circuit photovoltage Voc in these devices. And an explanation of t...

Limitations of surface photovoltage measurements

Surface photovoltage measurement used to measure the diffusion length of minority carriers in solar cells does not yield the correct value even when the cell thickness is much greater than the diffusion length. Under the best conditions the measured diffusion length is at least 10% lower than the actual value. The discrepancy increases as the ratio of diffusion length to thickness increases.

Effects of UV irradiation on the inverted surface layer in semiconductor‐insulator‐semiconductor devices

Irradiating semiconductor‐insulator‐semiconductor devices with 3650 A light increases the J0 associated with the minority‐carrier injection/diffusion current, resulting in a concomitant decrease in Voc. This increase in J0 is attributed to a decrease in carrier lifetime in the inverted surface layer as a result of UV irradiation.