Cubic inclusions in 4H-SIC studied with ballistic electron-emission microscopy

Using ballistic electron emission microscopy (BEEM), high-temperature- processing-induced 'double-stacking fault' cubic inclusions in 4H-Si-C were studied. BEEM is a three-terminal extension of scanning tunneling microscopy (STM) that can probe the local electronic transport properties of M/S interfaces with nanometer-scale spatial resolution and <10 meV energy resolution. It was found that measured spatial variations in the BEEM current were related to the inclusion orientation and local surface step structure. The observation of anomalously low schottky barrier height (SBH) suggested the existence of a triple-or quadruple-stacking fault inclusion.open3

Effect of inclined quantum wells on macroscopic capacitance-voltage response of Schottky contacts: Cubic inclusions in hexagonal SiC

Finite-element calculations of Schottky diode capacitance-voltage (C-V) curves show that an array of subsurface inclined quantum wells (QWs) produce negligible change in shape and slope of C-V curves, but significantly reduce the intercept voltage. This is particularly important for hexagonal SiC, in which current- or process-induced cubic inclusions are known to behave as electron QWs. These calculations naturally explain the surprisingly large effect of cubic inclusions on the apparent 4H-SiC Schottky barrier determined by C-V measurements, and together with the measured C-V data indicate the QW subband energy in the inclusions to be ~0.51 eV below the host 4H-SiC conduction band.open151

Quantum well state of self-forming 3C-SiC inclusions in 4H SiC determined by ballistic electron emission microscopy

High-temperature-processing-induced double-stacking-fault 3C-SiC inclusions in 4H SiC were studied with ballistic electron emission microscopy in ultrahigh vacuum. Distinctive quantum well structures corresponding to individual inclusions were found and the quantum well two-dimensional conduction band minimum was determined to be approximately 0.53 ?? 0.06 eV below the conduction band minimum of bulk 4H SiC. Macroscopic diode I-V measurements indicate no significant evidence of metal/semiconductor interface state variation across the inclusions.open292

Strain-free bulk-like GaN grown by hydride-vapor-phase-epitaxy on two-step epitaxial lateral overgrown GaN template

Crack-free bulk-like GaN with high crystalline quality has been obtained by hydride-vapor-phase-epitaxy (HVPE)growth on a two-step epitaxial lateral overgrown GaN template on sapphire. During the cooling down stage, the as-grown 270-μm-thick GaN layer was self-separated from the sapphire substrate. Plan-view transmission electron microscopyimages show the dislocation density of the free-standing HVPE-GaN to be ∼2.5×10 exp 7  cm exp −2 on the Ga-polar face. A low Ga vacancy related defect concentration of about 8×10 exp 15 cm exp−3 is extracted from positron annihilation spectroscopy data. The residual stress and the crystalline quality of the material are studied by two complementary techniques. Low-temperature photoluminescence spectra show the main neutral donor bound exciton line to be composed of a doublet structure at 3.4715 (3.4712) eV and 3.4721 (3.4718) eV for the Ga- (N-) polar face with the higher-energy component dominating. These line positions suggest virtually strain-free material on both surfaces with high crystalline quality as indicated by the small full width at half maximum values of the donor bound exciton lines. The E1(TO) phonon mode position measured at 558.52 cm exp −1 (Ga face) by infrared spectroscopic ellipsometry confirms the small residual stress in the material, which is hence well suited to act as a lattice-constant and thermal-expansion-coefficient matched substrate for further homoepitaxy, as needed for high-quality III-nitride device applications.Peer reviewe

Cubic inclusions in 4H-SiC studied with ballistic electron-emission microscopy

High-temperature-processing-induced “double-stacking fault” cubic inclusions in 4H-SiC were studied with ballistic electron emission microscopy (BEEM). Large BEEM current and a ∼0.53 eV local reduction in the Schottky barrier height (SBH) were observed where the inclusions intersect a Pt interface, confirming the quantum-well nature of the inclusions and providing nanometer scale information about local electronic behavior. Measured spatial variations in the BEEM current are related to the inclusion orientation and local surface step structure. An observation of an anomalously low SBH is discussed, suggesting the existence of a triple- or quadruple-stacking fault inclusion