Application of lateral photovoltage towards contactless light beam induced current measurements and its dependence on the finite beam size

Abstract

The nature of the signal due to light beam induced current (LBIC) at the remote contacts is verified as a lateral photovoltage for non-uniformly illuminated planar p-n junction devices; simulation and experimental results are presented. The limitations imposed by the ohmic contacts are successfully overcome by the introduction of capacitively coupled remote contacts, which yield similar results without any significant loss in the estimated material and device parameters. It is observed that the LBIC measurements introduce artefacts such as shift in peak position with increasing laser power. Simulation of LBIC signal as a function of characteristic length L(c) of photo-generated carriers and for different beam diameters has resulted in the observed peak shifts, thus attributed to the finite size of the beam. Further, the idea of capacitively coupled contacts has been extended to contactless measurements using pressure contacts with an oxidized aluminium electrodes. This technique avoids the contagious sample processing steps, which may introduce unintentional defects and contaminants into the material and devices under observation. Thus, we present here, the remote contact LBIC as a practically non-destructive tool in the evaluation of device parameters and welcome its use during fabrication steps.

An insight into optical beam induced current microscopy: Concepts and applications

“…Notably, the group detected the generated ac photovoltage from Si wafer, solar cell PN‐junction, non‐uniformly ion‐implanted junction, and partly‐deep junction capacitively without using any metal electrode directly in contact with the front surface of the semiconductor wafer. Similarly, Abhale et al demonstrated remote contact OBIC (RC‐OBIC) where the contacts are at several diffusion length away from the DUT (Abhale & Rao, 2014). In particular, the group compared the device parameters, for example, photo‐carrier spreading length and characteristic length, obtained through capacitive contacts and Ohmic contacts and found that both the techniques yielded similar results.…”

“…The screen generated laser of wavelength 500 nm, which enabled investigation of different photo-processes in different samples with a resolution of $1-2 μm. Similarly, Munakata et al (Munakata et al, 1982;Munakata & Matsubara, 1983) and Kinameri et al (Kinameri et al, 1988) (Abhale & Rao, 2014). In particular, the group compared the device parameters, for example, photo-carrier spreading length and characteristic length, obtained through capacitive contacts and Ohmic contacts and found that both the techniques yielded similar results.…”