Origin of noise in AlGaN∕GaN heterostructures in the range of 10–100MHz (original) (raw)
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Excess low-frequency noise in AlGaN/GaN-based high-electron-mobility transistors
Applied Physics Letters, 2002
The low-frequency 1/f noise characteristics of AlGaN/GaN high-electron-mobility transistors with gate length scaled down to 150 nm grown on sapphire by metalorganic chemical vapor deposition have been studied. Certain features of the 1/f noise have been revealed in these short-gate transistors. The low-frequency noise spectra show drastically different behavior depending on the gate voltage V G in the range of low (V Gt рV G р0) and high (V G ϽV Gt) biases. The noise spectra-gate bias dependences allow one to distinguish a spatial redistribution of effective noise sources in the transistor channel. The Hooge parameter has been deduced separately for the ungated region, ␣ H p Ӎ10 Ϫ3 , and for the gated region, ␣ H a Ӎ2ϫ10 Ϫ4 , of the transistor channel. These values are as low as those previously observed in nitride heterostructures grown on silicon carbide substrates.
Generation-recombination noise in GaN/AlGaN heterostructure field effect transistors
IEEE Transactions on Electron Devices, 2001
Local levels with a large activation energy 0 8-1.0 eV have been observed in low-frequency noise measurements of GaN/AlGaN heterostructure field effect transistors (HFETs and MOS-HFETs) grown on 4H-SiC substrates. The noise might come from thin (30 nm) AlGaN barrier layer. The estimates of the level parameters based on this assumption resulted in reasonable values of capture cross section (10 12 10 13 ) cm 2 and trap concentration 5 10 16 cm 3 .
Fluctuation and Noise Letters, 2001
The dependence of the 1/f noise on 2D electron concentration in the channel n Ch of AlGaN/GaN Heterostructure Field Effect Transistors and Metal Oxide Semiconductor Heterostructure Field Effect Transistors has been studied and compared. The dependencies of Hooge parameter α Ch for the noise sources located in the channel of the transistors on sheet electron concentration are found identical for both types of devices. The increase of the Hooge parameter α Ch with the decrease of the channel concentration observed in both types of devices confirms that the noise sources are located in the region under the gate in the AlGaN/GaN heterostructure and that electron tunneling from the 2D electron gas into the traps in GaN or AlGaN layers is a probable noise mechanism.
Low 1/f Noise in AlGaN/GaN HFETs on SiC Substrates
physica status solidi (a), 1999
Experimental results of the low-frequency noise measurements on a large number of different AlGaN/GaN High Electron Mobility Transistors (HEMTs) grown on sapphire and SiC substrates have been presented. In the HEMTs grown on sapphire, the 1af noise is an order of magnitude (or more) higher than for AlGaN/GaN HEMTs grown on SiC substrates. The devices on SiC substrates also have higher electron mobility compared to the devices grown on sapphire substrates. The temperature dependence of noise reveals a contribution to the noise from a local level with activation energy of approximately 0.42 eV for the structures grown on sapphire. A very weak temperature dependence of the low-frequency 1af noise found for the wafers grown on SiC is very important for high temperature applications of these devices.
On the low frequency noise mechanisms in GaN/AlGaN HFETs
Semiconductor Science and Technology, 2003
The low frequency noise in GaN/AlGaN heterostructure field effect transistors (HFETs) was studied in the temperature range from 8 to 300 K. At gate biases close to the threshold, the noise came from the device region under the gate, and the Hooge parameter α ch was inversely proportional to n s (α ∼ 1/n s ) in the entire temperature range. This dependence might be explained by electron tunnelling from the 2D gas into the traps in the adjoining GaN or AlGaN layers. At voltages close to zero, the ungated source-gate and gate-drain regions were responsible for the noise, and the Hooge constant was two orders of magnitude larger. This result is consistent with recent studies of the mechanism of the current collapse in GaN-based FETs. A notable contribution from the generation-recombination noise with activation energy 0.24 eV was observed in the temperature interval from 50 K to 150 K.
Low-Frequency Noise in SiO2/AlGaN/GaN Heterostructures on SiC and Sapphire Substrates
MRS Proceedings, 1999
The low-frequency noise in GaN-based Metal-Oxide-Semiconductor Heterostructure Field Effect Transistors (MOS-HFETs) and HFETs on sapphire and n-SiC substrates were studied. Hooge parameter at zero gate bias was calculated about 8 × 10−4 for both types of the devices. The AlGaN/GaN MOS-HFETs exhibited extremely low gate leakage current and much lower noise at both positive and negative gate biases. These features demonstrate the high quality of the SiO2/AlGaN heterointerface and feasibility of this technology for high-power microwave transmitter and high-power, high-temperature switches.
Influence of epitaxial structure in the noise figure of AlGaN/GaN HEMTs
IEEE Transactions on Microwave Theory and Techniques, 2000
The effect of noise figure of different AlGaN/GaN high electron-mobility transistor (HEMT) epitaxy structures is reported. The addition of a thin AlN layer between the barrier and channel gives better performance at biasings other than the best for minimum noise figure. However, varying Al composition in the HEMT barrier does not change the noise performance, contrary to a 2003 study by Lu et al. The measurements are checked with both the Pospieszalski and van der Ziel (Pucel) models. The models are used on six different samples, helping to reinforce the measurements and showing the strengths and weaknesses of each. Index Terms-AlGaN, GaN, high electron-mobility transistor (HEMT), noise figure, Pospieszalski, Pucel, van der Ziel.
Journal of Applied Physics, 2000
Low frequency noise has been investigated in gallium nitride/gallium-aluminum nitride GaN/ GaAlN field effect transistors grown on sapphire and silicon carbide ͑SiC͒ substrates under identical conditions. GaN/AlGaN heterostructures grown on SiC substrate have a lower level of 1/f noise and a higher electron mobility compared to samples grown on sapphire. The noise of the gate leakage current I g can give the main contribution to the output noise of the drain current I d even at I g /I d ratios as small as 10 Ϫ4 -10 Ϫ5 . For the structures grown on SiC, a very weak temperature dependence of the low frequency noise was found in the temperature range 300ϽTϽ550 K. For the structures grown on sapphire, the contribution of generation-recombination noise of the local level with energy activation ⌬Eϭ0.42 eV became important at TϾ320 K. The effect of band-to-band illumination on the low-frequency noise is similar to that for silicon and gallium arsenide ͑GaAs͒ based transistors. The Hooge parameter ␣ for the wafers grown on SiC can be as small as ␣ ϭ10 Ϫ4 . This value of ␣ is comparable with the value of ␣ for commercial GaAs field effect transistors.
Noise Spectroscopy of GaN/AlGaN HFETs
Noise characteristics of epitaxial n-GaN on sapphire layers and GaN/AlGaN on sapphire or SiC HFET structures were investigated in the temperature range from 13K to 300K. Ohmic contacts were made using Ti/Al/Ni/Au and contact noise was found negligible by TLM analysis. The Hooge parameter αH of epitaxial GaN was 2×10-3 at 300K, gradually decreasing to 10-4 around 50K. For GaN/AlGaN on sapphire HFET the g-r noise was dominant at almost every temperature, allowing only to determine αH = 2×10 -4 at 22K. The GaN/AlGaN on SiC HFETs were characterized by αH values of 10 -4 to 10-5.