GaN-on-Si transistors attract increasing interest for power applications. However, the breakdown behavior of such devices remains below theoretical expectations, for which the Si substrate is typically made responsible. In this work, the effect of the thickness of an aluminum nitride buffer layer on the vertical breakdown voltage, measured relative to a grounded silicon substrate, has been investigated. A voltage-polarity-dependent breakdown mechanism has been observed. It has been found that the breakdown in the positive bias voltage regime is initiated by carrier injection, for which the carriers originate from an inversion channel formed between the epitaxial layers and the p-silicon substrate. TCAD simulations have confirmed the proposed explanations, and suggest that appropriate modification of the electronic structure at the AlN/silicon interface could significantly improve the vertical breakdown voltage.

Articles you may be interested in X-ray characterization of composition and relaxation of Al x Ga 1 − x N ( 0 ≤ x ≤ 1 ) layers grown on GaN/sapphire templates by low pressure organometallic vapor phase epitaxy J. Appl. Phys. 108, 043526 (2010); 10.1063/1.3457149Oxygen induced strain field homogenization in AlN nucleation layers and its impact on GaN grown by metal organic vapor phase epitaxy on sapphire: An x-ray diffraction study Quaternary AlInGaN layers were grown on conventional GaN buffer layers on sapphire by metal organic vapour phase epitaxy at different surface temperatures and different reactor pressures with constant precursor flow conditions. A wide range in compositions within 30-62% Al, 5-29% In, and 23-53% Ga was covered, which leads to different strain states from high tensile to high compressive. From high-resolution x-ray diffraction and Rutherford backscattering spectrometry, we determined the compositions, strain states, and crystal quality of the AlInGaN layers. Atomic force microscopy measurements were performed to characterize the surface morphology. A critical strain value for maximum In incorporation near the AlInGaN/GaN interface is presented. For compressively strained layers, In incorporation is limited at the interface as residual strain cannot exceed an empirical critical value of about 1.1%. Relaxation occurs at about 15 nm thickness accompanied by strong In pulling. Tensile strained layers can be grown pseudomorphically up to 70 nm at a strain state of 0.96%. A model for relaxation in compressively strained AlInGaN with virtual discrete sub-layers, which illustrates the gradually changing lattice constant during stress reduction is presented. V C 2012 American Institute of Physics. [http://dx.

InGaN is a promising material for direct solar water splitting due to its tuneable bandgap between 0.69 and 3.4 eV. Several investigations were carried out recently to test the suitability of InGaN in photoelectrochemical cells (PECs). These studies were performed in a multitude of different electrolytes and hence a comparison of the results is very difficult. Therefore, the electrochemical stability of InGaN was investigated and compared in different commonly used electrolytes in this work. The InGaN layers were deposited via metal-organic vapour phase epitaxy (MOVPE). Their structural properties were examined by high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The long-term stability of the InGaN layers was studied in NaCl, HCl, HBr, H 2 SO 4 , NaOH and KOH. Etching was observed for the two bases after 48 h. Furthermore, the photoanodes were investigated via chronoamperometry. For these measurements, the samples were illuminated with a 55 W Xe lamp for 45 min and additionally biased with 0.5 V. A comparison of the different electrolytes reveals that only the samples in NaOH and HBr show a sufficient photocurrent. Additionally, stable InGaN surfaces were observed only in 1 mol/L NaCl and in 1 mol/L HBr. Since the use of HBr most likely leads to the formation of Br 2 instead of O 2 , it is concluded that n-doped InGaN has to be used with co-catalysts in PECs to prevent the etching of the surface.

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