LOW-FREQUENCY NOISE IN N-GAN

Low-frequency noise has been investigated in the hexagonal polytype of n-type gallium nitride (GaN) with equilibrium electron concentration at 300 K n(0) similar or equal to 7x10(17) cm(-3). The frequency and t emperature dependence of the noise spectral density S-I/I-2 was studie d in the range of analysis frequencies f from 20 Hz to 20 kHz in the t emperature range from 80 to 400 K. Over the entire temperature range t he frequency dependence of the dark noise is close to S-I/I-2 similar to 1/f (flicker noise). The rather weak temperature dependence of the noise level is characterized by very high values of the Hooge constant alpha similar or equal to 5-7. These large alpha values indicate a ra ther low level of structural quality of the material. The effects of i nfrared and band-to-band illumination on low-frequency noise in GaN ar e studied here for the first time. The noise level is unaffected by il lumination with photon energy E-ph<E-g (E-g is the band gap) even for a relatively high value of the photoconductivity Delta sigma/sigma sim ilar or equal to 50%. Band-to-band illumination (E(ph)greater than or equal to E-g) influences the low-frequency noise level over the entire investigated temperature range, At relatively high temperatures the i nfluence of illumination is qualitatively similar to that of band-to-b and illumination on low-frequency noise in Si and GaAs. At relatively low temperatures the influence of illumination on the noise in GaN is qualitatively different from the results obtained earlier for Si and G aAs. (C) 1998 American Institute of Physics.