High phosphorous incorporation in (100)-oriented MP CVD diamond growth

Abstract

Diamond n-type layers are crucial for the development of a new bipolar diamond-based electronic technology. However, the difficulties to incorporate impurity atoms into the diamond lattice make its growth a stage of technological research still in progress. Phosphorus doping has been carried out successfully on (111)-oriented diamond substrates, reaching high concentrations and good reproducibility. Nevertheless, such reproducible results have not been obtained for the (100) growth orientations yet, even though the (100) substrate orientation is still the most used diamond substrate for electronic applications.

In this study, three samples are grown by microwave plasma-enhanced chemical vapor deposition on diamond (100)-oriented high pressure high temperature substrates. All samples are deposited with the same growth conditions except methane, which was varied between 1.5 % and 3.5 %. A different growth mechanism is observed for each of the methane content used. The step flow growth mechanism shows increased phosphorus incorporation, determined by cathodoluminescence (CL) in cross sectional view in focused ion beam preparations. This sample also shows a less rough surface and no crystal defects observable by transmission electron microscopy (TEM). That is why these growth conditions are used for the fabrication of the n-type layer of a p(+)/p(-)/n stack. Ellipsometry and TEM measurements on this sample yield a high growth rate of 3.5 mu m/h with a phosphorus concentration of 4 x 10(17) cm(-3), estimated by CL spectroscopy. The sample shows a low density of surface defects, observed by optical microscopy. However, TEM observations show dislocations with 1/2 a < 110 > burger vector and stacking faults with 1/3 < 111 > displacement vector.