Browsing by Author "Desmaris, V."

Now showing 1 - 2 of 2

DC and microwave performance of AlGaN/GaN HEMTs passivated with sputtered SiNx
(2007-07-01)
Shiu, J. Y.
;
Desmaris, V.
;
Rorsman, N.
;
Kumakura, K.
;
Makimoto, T.
The effects of sputtered and room temperature plasma enhanced chemical vapour deposition (RT-PECVD) SiNx passivation on the dc and microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs) are studied. The pulsed I - V characteristics from a class B quiescent bias point and transient measurements indicate that the sputtered SiNx passivation is more efficient in suppressing lag effects in AlGaN/GaN HEMTs. Dispersion-free sputtered SiNx passivated AlGaN/GaN HEMTs were obtained using this technique. Continuous-wave (CW) measurements without active cooling give a maximum output power density of 6.6 W mm(-1) at V-gs=- 4 V, V-ds = 50 V and a maximum power added efficiency of 51.3% at V-gs=- 4 V, V-ds = 30 V at 3 GHz on 2 x 50 mu m AlGaN/GaN HEMTs on the sapphire substrate, with a gate length of 2 mu m and without field-plated gates. To the best of our knowledge, this is the highest level power density reported on the sapphire substrate without field-plate design. The extrinsic cut-off frequency (f(t)) and maximum oscillation frequency (f(max)) are 51 GHz and 100 GHz, respectively, on 2 x 50 x 0.15 mu m HEMTs. To our knowledge, the sputtered SiNx passivation for AlGaN/GaN HEMTs is a unique technique, which has never been published before.
Influence of oxynitride (SiOxNy) passivation on the microwave performance of AlGaN/GaN HEMTs
(2008-05-01)
Desmaris, V.
;
Shiu, J. Y.
;
Rorsman, N.
;
Zirath, H.
;
Chang, E. Y.
The effects of the composition of oxynitride passivations (SiOxNy) deposited by plasma enhanced chemical-vapor deposition (PECVD) at room temperature on the microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. Five different SiOxNy passivating layers were deposited covering the whole range of dielectrics combinations from SiOx to SiNy. Their impacts on the HEMT performance were studied by means of DC, S-parameters, pulsed IV and load-pull measurements. The oxynitride dielectric with a refraction index of 1.58 was shown to be an effective SiOxNy passivation for limiting the gate-lag effects in the HEMTs and at the same time increasing the breakdown voltage of the device. It is thus a promising passivation layer for microwave power high voltage and high power applications. (c) 2007 Elsevier Ltd. All rights reserved.