No abstract

No abstract

In the present work, AlGaN/GaN quantum wells and High Electron Mobility Transistors (HEMTs) have been grown by molecular beam epitaxy on Si(111) and GaN on sapphire templates. The optical quality and the electrical properties were studied by low temperature photoluminescence and Hall effect. These measurements attest the quality of these heterostructures and demonstrate the high on-wafer uniformity of the materials grown on 50 mm wafers, and this even for the III-nitrides grown on Silicon.1 Introduction In recent years, the Molecular Beam Epitaxy (MBE) has begun to demonstrate potentialities to realize high quality GaN based heterostructures for electronics as well as optoelectronic applications. Beyond the achievement of high quality GaN based heterostructures, MBE is now dealing with other process considerations such as reproducibility and uniformity on various substrates like sapphire, silicon carbide or silicon. In order to address this latter point, AlGaN/GaN quantum wells (QWs) and HEMT heterostructures have been grown with a Riber MBE reactor designed for the growth of IIINitrides materials. Ammonia was used as nitrogen source, whereas effusion cells supplied group III elements. The growth were performed on 50 mm Si(111) wafers and on 50 mm MOCVD grown GaN on sapphire templates. The layer optical properties were assessed by using low temperature photoluminescence (PL) performed across the wafers, whereas the electrical quality was studied by Hall effect after the realization of van der Pauw cloverleaf and Hall bar devices. The effect of heteroepitaxial growth on the layers quality was studied by comparing results obtained on Silicon with those obtained on the low defect density GaN templates.

Subject classification: 78.30.Am; 78.66.Db; S5The optical transmittance and reflectance of heavily boron-doped (2 Â 10 20 cm --3 < [B] < 2 Â 10 21 cm --3 ) epitaxial diamond layers deposited by MPCVD were measured in the infrared range. While T-dependent measurements confirmed the metallic character of such films, the overall spectral features were well reproduced by introducing Drude components in the fitting expression for the optical conductivity. The associated microscopic transport parameters were quantitatively compared to those resulting from preliminary transport measurements performed on the same samples. We show that room-temperature FTIR reflectance measurements provide an easy contactless characterization of the transport properties of such p + films, and we discuss what new information on carrier-phonon interaction as well as on the transport mechanism in the impurity band might be gained from temperature-dependent spectroscopic data.

No abstract