The small-signal equivalent circuit of AlGaN/GaN HEMT is discussed It is shown that an extremely high gate voltage has to be applied to correctly determine series resistances. Effects appearing at high forward gate voltages are discussed. Good agreement between measured and simulated data has been achieved.

We report on compositional fluctuations in GaN/GaInN/GaN double heterostructures investigated by photoluminescence excitation and resonant Raman spectroscopy. The energy and line-shape of both luminescence and longitudinal optical (LO) phonon Raman peaks strongly depend on excitation energy due to selective excitation of regions with different In content. For a given excitation energy, luminescence from In-rich regions takes place and in addition, with increasing sample temperature, resonantly excited luminescence from regions of lower In content is superposed. Thus, the luminescence strongly broadens and on average shifts to higher energies with increasing temperature. The spectral variation of the photoluminescence and Raman cross sections is determined and correlated with the GaInN absorbance as measured by photothermal deflection spectroscopy.

No abstract

No abstract

No abstract