Surface conductivity enhancement of H-terminated diamond based on the purified epitaxial diamond layer

Abstract

Diamond-based semiconductor with high electrical conductivity is a key point in diamond device development. In this paper, a thin single-crystal diamond layer of high quality was epitaxially grown on a commercial tool-grade diamond seed by incorporating active O atoms from the typical growth environment. Subsequently the Htermination density was enhanced on the diamond surface by exposure to the pure hydrogen plasma, and the surface conductivity of H-terminated diamond was analyzed in detail. The thin epitaxial layers on the high pressure high temperature (HPHT) diamond seeds show lower resistance than the ones on the chemical vapor deposition (CVD) diamond seeds, which could be comparable with the lowest values reported. After the thin diamond layers were grown with and without addition of O 2 , the carrier mobility in the conductive channel increase to almost 80 cm 2 •V-1 •s-1 under O 2 contained condition, much higher than those without O 2 incorporation. The ionization scattering is dominant to the carrier mobility compared with the surface scattering. The higher carrier mobility is attributed to the lower impurity density in the epitaxial layer, which is because the active O atoms could purify the epitaxial layer by removing or reducing Si and N related impurities.

Carrier mobility enhancement on the H-terminated diamond surface

“…That means that, the epitaxial diamond layers of sample 2 and sample 3 are purified when using the oxygen addition in the plasma environment compared with the CVD diamond substrate. It is due to the reaction between O atoms and N atoms in the chamber and impurity N atoms will be exhausted [21][22] . Little intensity differences between the epitaxial layer and the substrate for sample 1 in the PL spectra are mainly because the epitaxial layer were almost ground off during the polishing.…”

“…Three 5mm╳5mm commercial CVD single crystal diamond samples with general quality were used as the substrates. And then the high quality layers with thickness of about 100um were grown on the CVD diamond substrates by the plasma purification technology [21] . A certain amounts of O atoms were used to exhaust the nitrogen and silicon impurity atoms in the plasma environment, which could purify the diamond crystal structure.…”

Investigation of charge carrier trapping in H-terminated diamond devices

“…In addition, the two-dimensional p-type conductive channel formed by H-termination offers a unique platform for fabricating FETs for high frequency applications [15]. However, the surface conductivity of the H-terminated channel is found to be highly dependent on the surface quality [16], suggesting that recombination and trapping at interfaces and junctions may play a critical role. In order to successfully leverage diamond's outstanding properties, we study charge carrier transport dynamics and find that the properties of diamond devices exhibiting negative capacitance can be tuned by varying the device geometry.…”