Electrical Transport Mechanisms in p⁺a-SiC:H/n c-Si Heterojunctions: dark J-V-T Characteristics

Abstract

In the present paper we show results of dark current-voltage measurements performed on p+ a- SiC:H/n c-Si heterojunction diodes at various temperatures (100–400K). We investigated the voltage derivative of these J-V curves in order to the distinguish possible current transport mechanisms. It was found that for low temperatures (<300K), the current is determined by recombination of carriers in the crystalline silicon, whereas at high temperature (>300 K), by a tunnelling mechanism. At room temperature, both mechanisms contribute to the current. By using an equivalent circuit model and detailed numerical simulations we have interpreted our experimental characteristics. The simulations done at room temperature, show that at low forward bias voltage the current is controlled by recombination in the crystalline silicon and that at high forward bias voltage by a combination of multi-step tunnelling and a-SiC:H series resistance. For interface state densities equal to or higher than 1012 cm−2, the recombination was found to be dominated by the states at the amorphous-crystalline silicon interface.

Current transport mechanisms in n-type amorphous silicon-carbon on p-type crystalline silicon (a-:H/c-Si) heterojunction diodes

“…However, this result contrasts with Magafas et al [6] who found diffusion-recombination (in the crystalline silicon) mechanisms in undoped a-SiC/p c-Si heterojunctions for applied voltages lower than 0.4 V and temperatures higher than 250 K. On the other hand, in p + a-SiC/n c-Si heterojunctions different transport mechanisms have been found, for instance thermal injection [4] and tunnelling [13] for temperatures higher than 300 K and low forward voltages (V < 0.6 V). Notice that these transport mechanisms are not observed in our samples throughout the range of measured temperatures and biases.…”

Temperature Dependence of Amorphous/Crystalline Silicon Heterojunction Solar Cells

“…van Cleef et al evaluated the current-voltage characteristics of the thin (10 nm) p þ a-SiC:H/n c-Si heterojunction at various temperatures (100 -400 K), and concluded that the current in their device was determined by either recombination current or tunneling current depending on the temperature. 16) Jensen et al examined n a-Si:H (12.5 nm)/p c-Si heterojunction solar cells and explained that the forward current of their device was dominated by the diffusion current in the c-Si region. 7) Because the a-Si:H layers in these experiments were very thin, the junction property seemed to be determined by the c-Si layer where the depletion zone mainly spreads.…”

Ion Beam Synthesis of SiC/Si Heterostructures by Mevva Implantation

“…In fact, all the implanted samples, as-implanted or annealed, show rectifying behaviors. Information on the transport mechanisms can be obtained from the temperature variation of the voltage derivative of the I-V characteristics [ 16,17]. Details of these analyses will be presented elsewhere [16,18].…”