We successfully fabricated a template with an air tunnel between a patterned sapphire substrate (PSS) and GaN using a photoresist mask. The photoresist mask was subjected to plasma etching to induce the growth of the GaN nucleus at the top of the mask by exposing only the top of the PSS lens to the mask height. The carbon profile of the photoresist mask was checked by secondary ion mass spectrometry to detect the presence or absence of carbon in the GaN template during the process. In order to confirm the carbon’s effect on the epitaxially grown GaN template, the XRD was confirmed by the pole figure and the rocking curve. In order to confirm the change of the energy level of GaN by forming a trap in the energy band by carbon, we confirmed the effect of the carbon by comparing the degree of pure GaN.

Screen printing technique followed by firing has commonly been used as metallization for both laboratory and industrial based solar cells. In the solar cell industry, the firing process is usually conducted in a belt furnace and needs to be optimized for fabricating high efficiency solar cells. The printed-Al layer on the silicon is rapidly heated at over 800°C which forms a layer of back surface field (BSF) between Si-Al interfaces. The BSF layer forms p-p + structure on the rear side of cells and lower rear surface recombination velocity (SRV). To have low SRV, deep p + layer and uniform junction formation are required. In this experiment, firing process was carried out by using conventional tube furnace with N2 gas atmosphere to optimize Voc of laboratory cells. To measure the thickness of BSF layer, selective etching was conducted by using a solution composed of hydrogen fluoride, nitric acid and acetic acid. The Voc and pseudo efficiency were measured by Suns-Voc to compare cell properties with varied firing condition.