The current and frequency dependencies of the low frequency noise have been investigated in 4H-SiC p+-n junctions in the frequency range 100-104 Hz and at current densities from 10-4 to 101 A/cm2. Good quality of the p+-n diode under investigation has been ascertained by high value of the recombination time in the space charge region, &tgr;R ≈ 70 ns, extracted from current voltage characteristic. At small current densities j ⩽ 10-3 A/cm2, the spectral noise density SI ∝1/f3/2. At 10-3 A/cm2 < j < 10-2 A/cm2, the generation-recombination (GR) noise predominates. The amplitude of this GR noise non-monotonically depends on current. At j ⩾ 10-2 A/cm2, the 1/f (flicker noise) is dominant. A new model of GR noise of the recombination current in forward biased
p-n junction has been proposed. The model assumes that a trap level located relatively close to the conduction band is responsible for the observed GR noise. The main contribution to the GR noise comes from the fluctuations of the charge state of the trap. The model describes well both current and frequency dependencies of the observed GR noise.
Low frequency noise in 4H-SiC BJTs with the current gain β ≈ 10-15 and unity current gain frequency fT of about 1.5 GHz has been investigated. The corner frequency fc was found to be fc = 2×104 Hz. The value of the coefficient KB,
which is the figure of merit for the low frequency noise in the region of noise proportional to squared current, was found
to be 6×10-7 μm2. This value is only an order of magnitude higher than the typical values for high-frequency Si-BJTs.
The nature of the 1/f noise in GaN/GaAlN Heterostructure Field Effect Transistors (HFETs) has been discussed. New experimental results on the 1/f noise in GaN/GaAlN HFETs and different models on the flicker noise have been also described. It has been demonstrated that the 1/f noise in GaN/GaAlN HFETs might be linked to the electron tunneling from the 2D gas into the tail states in GaN or AlGaN layers.
Generation-recombination (GR) noise in GaN and AlGaN thin films, GaN based Metal Semiconductor Field Effect Transistors (MESFETs), Heterostructure Field Effect Transistors (HFETs) and Schottky diode photodetectors was investigated. AlGaN thin films, AlGaN/GaN HFETs and Schottky barrier Al0.4Ga0.6N diodes exhibited GR noise with activation energies of 0.8 - 1 eV. AlGaN/GaN HFETs also presented GR noise with activation energies of 1 - 3 meV and 0.24 eV at cryogenic temperatures. No such noise was observed in thin doped GaN films and GaN MESFETs. GR noise with the largest reported activation energy of 1.6 eV was measured in AlGaN/InGaN/GaN Double Heterostructure Field Effect Transistors (DHFETs). We conclude that the local levels responsible for the observed noise in HFETs and DHFETs could be located in AlGaN barrier layers.
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