Effects of residual C impurities and Ga vacancies on the dynamic instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron mobility transistors are investigated. Secondary ion mass spectroscopy, positron annihilation spectroscopy, steady state and time-resolved photoluminescence (PL) measurements have been performed in conjunction with electrical characterization and current transient analyses. The correlation between yellow luminescence (YL), C-and Ga vacancy concentration is investigated. Timeresolved PL indicating the C N O N complex as the main source of the YL, while Ga vacancies or related complexes with C seem not to play a major role. The device dynamic performance is found to be significantly dependent on the C concentration close to the channel of the transistor. Additionally, the magnitude of the YL is found to be in agreement with the threshold voltage shift and with the on-resistance degradation. Trap analysis of the GaN buffer shows an apparent activation energy of ∼0.8eV for all samples, pointing to a common dominating trapping process and that the growth parameters affect solely the density of trap centres. It is inferred that the trapping process is likely to be directly related to C based defects.The AlGaN/GaN material system is a fundamental building-block for the fabrication of high-power GaN on Si metal insulator semiconductor high electron mobility transistors (MIS-HEMTs). 1,2 Despite the large lattice and thermal coefficient mismatch, Si is widely used as the substrate of choice for nitride-based HEMTs. Complex multilayer structures are needed in order to maintain the strain during the growth, at the same time the structure should provide high electrical resistance and low leakage currents. One way to satisfy these requirements, is to introduce acceptor-like impurities, e.g. Fe or C [3 and 4]. However, Fe is considered as non-suitable element in the front-end-of-line Si area, limiting the integration possibilities in low-cost environments. Carbon on the other hand, could potentially fulfill the task as it acts as a source of donor compensation centers, while being Si environment friendly. For efficient GaN based devices, it is of uttermost importance to reduce, or avoid trapping related failures such as current collapse, dynamic on-resistance (R DSON ) degradation and threshold voltage (V th ) shifts.The location of the traps causing dynamic instabilities in the HEMT structure is still under debate. Some studies 5,6 indicated that trapping occurs solely in the buffer due to C-doping, while others showed that the trapping takes place at the interface between the dielectric and the III-nitride semiconductor. 7,8 Combinations of the two previously mentioned processes have also been proposed. 9 A clear attribution of the yellow luminescence (YL) band around 2.2 eV in GaN-related materials systems to a single species or defect has been under discussion for long time. 10 Previously, it has been argued that Ga vacancies (V Ga ) accompanied by C or O could be responsible for the YL...

In this work, low temperature growth of GaAs epitaxial layers on Ge substrates by metalorganic vapor phase epitaxy has been studied. The experiments show that a growth temperature of 530°C and a V/III ratio of 3.5 result in smooth GaAs surfaces. Atomic force micrographs do not show any anti-phase boundaries on the surface of GaAs grown on a misoriented substrate. X-ray diffraction curves show that the layer tilt is reduced as the growth temperature is lowered. Synchrotron X-ray topography reveals very low threading dislocation densities of 300 cm-2 for the GaAs epitaxial layers. Additionally, no misfit dislocations are observed. If a single layer is deposited at low temperature, secondary ion mass spectrometry shows a considerably reduced arsenic diffusion into Ge. When an additional layer is deposited at higher temperature on top of the initial low temperature layer, a substantial increase for the deep concentration-dependent arsenic diffusion is found.

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