Estimation of the p-n Junction Depth in LWIR HgCdTe Detectors from the Spatial Profile of the Lateral Photocurrent and Transverse Photovoltage Induced by an Infrared Small Spot
Authors: Garber, V.; Dust, A.; Baskin, E.; Spektor, B.; Bahir, G.
Source: Journal of Electronic Materials, Volume 30, Number 6, 1 June 2001 , pp. 690-695(6)
Abstract:A new, simple nondestructive procedure for the estimation of the junction depth in planar long wavelength HgCdTe photodiodes is presented. The technique uses a combination of scanning light beam-induced current data with a transversal photovoltage measurement to extract the junction depth. The technique is applicable to both homojunction and heterojunction diodes. It is assumed that in the cross-section perpendicular to the device surface, the junction has a two-dimensional structure, and the length of the vertical junction is treated as the junction depth. The spatial profile of the lateral photocurrent produced by the spot scan marks the boundaries of the horizontal junction. Of these boundaries, only one of the vertical junctions contributes to the photocurrent. Using weakly absorbed infrared light insures the homogeneous profile of the photogenerated carriers along the vertical junction. A uniformly irradiated vertical junction produces the transverse photovoltage between its terminals. When the remote contacts are grounded, this photovoltage is dependent on the series resistance between the junction and the contacts. In the case when the circuit between the remote contacts is opened, the current is zero, and the photovoltage reaches its maximum value, equal to the junction open circuit voltage. From comparison of the two voltages, we extract the value of the series resistance. We have derived an analytical expression for the series resistance, which includes the junction depth. Comparison between the observed RS values and those of the analytical expression, enable us to extract the junction depth value. The validity of the method is shown using a two-dimensional numerical simulation, and experimentally from ion-implanted and diffused p-n junctions.
Document Type: Research Article
Publication date: 1 June 2001