On conductivity type conversion of p-type silicon exposed to a low-frequency inductively coupled plasma of Ar + H₂

Abstract

The treatment of an Ar + H2 plasma generated by a low-frequency inductively coupled plasma system at 500 °C introduces an n-type region (of average electron concentration ∼1015 cm−3) on a Czochralski p-type substrate, forming a deep p–n junction. Examination by an electron microscope shows that the plasma treatment produces uniform nanocones on the surface and some defects, such as dislocations and platelets, in the subsurface. All these observed results are hydrogen-related. The conductivity type conversion is due to the formation of hydrogen-enhanced oxygen-related thermal donors (OTDs) as well as hydrogen-incorporated shallow thermal donors. The OTD-related signals are directly observed in the infrared absorption spectra. Both donors are annihilated after annealing at 550 °C for 10 min, resulting in conductivity recovery from n-type to original p-type. The electrical properties of the as-formed junction are investigated using current versus voltage (I–V), capacitance versus voltage (C–V) and Hall effect measurements. On this basis, the junction depth, carrier profile and hydrogen diffusion behaviour are studied. Moreover, a clear photovoltaic effect of the junction has been observed through the Suns-Voc and illuminated I–V tests.

High‐Density Plasma‐Enhanced Chemical Vapor Deposition of Si‐Based Materials for Solar Cell Applications

“…are expected. In principle, the neutral particles will become more and more important among species contributing to the film deposition due to the enhanced ion recombination with increasing distance d. It was recognized that the severe etching and ion bombardment produces additional defects on growing surface/substrate directly contacting with the high-density plasma [16]. Therefore, the deposition region should avoid direct contact with the high-density plasma during deposition.…”

“…Low-temperature (100-200 °C) and high-rate (>1 nm/ S) deposition of nc-Si in the direct plasma region of LFICP have been realized [15]. In our previous works [16,17], it was also found that the severe etching on silicon surface directly exposed to the high-density hydrogen containing plasma drastically changes the morphology and microstructures of the surface. As a consequence, it is very easy to attain μc-/nc-Si:H with a high deposition rate.…”

Crystalline silicon surface passivation by intrinsic silicon thin films deposited by low-frequency inductively coupled plasma

“…Using this method, the maximum effective lifetime value of 53 ls was obtained on p-type silicon substrate (resistivity 1-20 X cm) with a 15 nm thick a-Si:H passivation layer. In our previous works, we reported the development of low frequency inductively coupled plasma (LFICP) source 9 and its applications in nanotechnology fabrication 10,11 and also, the deposition of intrinsic and doped silicon thin films. 12,13 It was acknowledged that this LFICP source features various inherent advantages such as a high density, axial/radial uniformity plasma, and also independent control of electron number density and the energy of ions impinging on the growing surface.…”

Highly Efficient Silicon Nanoarray Solar Cells by a Single‐Step Plasma‐Based Process

“…p-n type conversion. [ 22 ] The dependencies of the photovoltaic responses (opencircuit voltage V OC and density of short-circuit current I SC , fi ll factor, and photo-conversion effi ciency of the solar cell (produced using Si samples formed at a substrate temperature of 500 ° C, bias voltage -50 V, discharge power 2 kW, and plasma treatment time 30 min) on the resistivity of the Si wafer are shown in Figure 3 . These graphs clearly illustrate that the wafer resistivity (controlled by the doping) can serve as an additional effective tool for the precise tuning of the solar cell properties.…”

“…As a result, a boron-depleted sub-surface layer is formed. Second, after partial removal of boron-related acceptor sites, an n-type layer is formed due to the hydrogen-assisted formation of oxygen-related thermal donors and shallow thermal donors [ 22 ] (note that thermal donors are able to compensate the boron doping in Si [ 25 ] ). Besides, Si-H-Si centres which act as donors can be formed in Si.…”