AlGaN/GaN high electron mobility transistors on 100 mm silicon substrates by plasma molecular beam epitaxy

Abstract

GaN high electron mobility transistor (HEMT) structures have been grown by plasma molecular beam epitaxy on 100 mm diameter ⟨111⟩ silicon substrates. Crack-free films with thicknesses of up to 1.7 μm were deposited without the use of strain-relaxing buffer layers. X-ray measurements indicate high structural uniformity and the Pendellosung oscillations are observed due to the abruptness of the AlGaN/GaN interface. Capacitance-voltage measurements display a sharp pinch-off with a depleted GaN buffer layer and no measurable charge accumulation at the substrate-epi interface. Transmission line measurements on the GaN HEMT buffer and substrate indicate a loss of less than 0.2 dB/mm up to 20 GHz. An average sheet resistance of 443 Ω/sq with a standard deviation of 0.8% and a mobility of 1600 cm2/V s were obtained for an Al0.25Ga0.75N/GaN HEMT. Transistors were fabricated with a current density of 1.2 A/mm and a transconductance of 290 mS/mm which is quite comparable to GaN HEMTs on SiC.

Development of technological building blocks for the monolithic integration of ammonia-MBE-grown GaN-HEMTs with silicon CMOS

“…Besides, the effect of growth temperature on silicon diffusion arising from the substrate into grown layers is confirmed. This is consistent with the low silicon content (below 1 × 10 15 cm −3 ) obtained in when growing at even lower temperature (750 °C) using plasma‐source MBE.…”

“…In particular, plasma‐MBE allows to grow AlGaN/GaN heterostructures in Ga‐rich conditions at temperatures as low as 750 °C . Such a strategy has proved to be very efficient to limit the diffusion of dopant in the CMOS active regions as well as the silicon diffusion arising from the substrate into the GaN buffer .…”

Growth and characterization of AlGaN/GaN HEMT heterostructures on 100-mm Si (111) by MBE

“…However, excess Ga on the GaN surface in the metal-rich growth regime produced streaky RHEED patterns with smooth 2D growth morphologies and improved crystalline quality. Since both the rough surface morphology and the poor quality are undesirable for device epilayers, GaN layers grown in the metal-rich growth regime have been successfully utilized in the development of both Ga-polar and N-polar HEMTs for their unique advantages [116,153,192]. In addition, we have also demonstrated Ga-polar AlGaN/GaN HEMTs grown in the metal-rich growth regime [151,152] as discussed in Section 4.6.…”

“…using PA-MBE[153] compared to ammonia MBE. Thus, it becomes necessary to introduce stress mitigating layers to alleviate the thermal mismatch induced tensile strain and obtain crack-free GaN by ammonia MBE.The choice of stress mitigating layers for GaN growth on Si should yield efficient tensile strain compensation, smooth surface morphology and lower dislocation density such that GaN material properties become suitable for HEMT applications.…”

Studies on GaN based HEMT heterostructures on 100-mm silicon grown by molecular beam epitaxy

“…However, final metal rich growth conditions result in Ga accumulation and droplet formation. To desorb the excess gallium, growth with growth interruption has been implemented by various groups [68][69][70]75]. During the growth interruption, accumulated 'Ga' gets evaporated and provides with smooth GaN surface for the subsequent growth.…”