This novel technique involves the ultraviolet (UV) lamp-assisted photoelectrochemical etching of n-type 3C- and 6H-SiC for device processing. In order for this method to be effective, the UV light must be able to enhance the production of holes in the SiC during the etching process thus providing larger currents with light from the photocurrents generated than those currents with no light. Otherwise dark methods would be used as in the case of p-type 3C-SiC.
Experiments have shown that the I/V characteristics of the SiC-electrolyte interface reveal a minimum etch voltage of 3 V and 4 V for n- and p-type 3C-SiC, respectively. Hence, it is possible for etch-stops to occur. From Auger spectroscopy, an oxide formation is present on n-type 3C-SiC where after etching a yellowish layer corresponds to a low silicon to carbon (Si/C) ratio with large photocurrents and a white layer corresponds to a high Si/C ratio with small photocurrents. P-type 3C-SiC shows a grayish or silver layer with a high Si/C ratio and a green layer with a low Si/C ratio. Additionally, n-type 6H-SiC shows a brown or blue layer with a minimum etch voltage of 3 V.
The colors of the etched regions of SiC represent layers that have some degree of porousity formed by the electrochemical process. As a result, the photo-excitation allows control of the porousity and changes the electrical properties of SiC. The nature of these porous layers with its increased resistivity can lead to the formation of devices.