MOVPE growth of GaN on 6-inch SOI-substrates: effect of substrate parameters on layer quality and strain

Abstract

We demonstrate that higher crystalline quality, lower strain and improved electrical characteristics can be achieved in gallium nitride (GaN) epitaxy by using a silicon-on-insulator (SOI) substrate compared to a bulk silicon (Si) substrate. GaN layers were grown by metalorganic vapor phase epitaxy on 6-inch bulk Si and SOI wafers using the standard step graded AlGaN and AlN approach. The GaN layers grown on SOI exhibited lower strain according to x-ray diffraction analysis. Defect selective etching measurements suggested that the use of SOI substrate for GaN epitaxy reduces the dislocation density approximately by a factor of two. Furthermore, growth on SOI substrate allows one to use a significantly thinner AlGaN buffer compared to bulk Si. Synchrotron radiation x-ray topography analysis confirmed that the stress relief mechanism in GaN on SOI epitaxy is the formation of a dislocation network to the SOI device Si layer. In addition, the buried oxide layer significantly improves the vertical leakage characteristics as the onset of the breakdown is delayed by approximately 400V. These results show that the GaN on the SOI platform is promising for power electronics applications.

Atomic layer etching of gallium nitride (0001)

“…11 Recent advances in III-N semiconductors also call for atomic scale control of etch processes and defect free nanofabrication. Metal organic vapor phase epitaxy (MOVPE) grown AlGaN/GaN heterostructure high electron mobility transistors (HEMTs) have a well-defined layered structure with the two-dimensional electron gas (2DEG) 12,13 and can benefit greatly from recessed gates which allow more powerful modulation of the 2DEG. [14][15][16] Etching of the gate recess is challenging as conventional reactive ion etching (RIE) does not provide sufficiently good control over the etch process, and high energy ions can cause damage to the 2DEG layer.…”

MOVPE growth of GaN on patterned 6-inch Si wafer

“…Thimethylaluminium (TMAl), thimethylgallium (TMGa) and ammonia (NH 3 ) were used as precursors for aluminium, gallium and nitrogen, respectively. Hydrogen was used as the carrier gas, more details can be found in [5]. Figure 3 presents cross-sectional SEM image of the structures grown on non-patterned Si substrates.…”

“…An optical in-situ measurement system was used to assess the growth rate and wafer surface temperature profile. A more detailed measuring mechanism description is explained in detail in [5]. Besides an optical in-situ measurements, the thickness measurements were verified with cross-sectional scanning electron microscope (SEM).…”

“…By inserting different Al x Ga 1−x N interlayers, compressive stress is introduced to compensate the tensile stress produced during the cooling process to eliminate surface cracking. The growth on silicon-on-insulator (SOI) substrate allows using significantly thinner AlGaN buffer layer compared with the growth on bulk Si [5], however build-up of stresses during epitaxy results in GaN cracking at thicknesses exceeding 1μm. Recently, the thin AlN transition layer grown on Si by plasma-enhanced atomic layer deposition (PEALD) has been demonstrated [6].…”

Aluminum Nitride Transition Layer for Power Electronics Applications Grown by Plasma-Enhanced Atomic Layer Deposition

“…However, the high temperatures required for epitaxial growth, mismatches in the lattice and thermal expansion coefficient can result in the formation of numerous dislocations or even cracks in the GaN film on account of large tensile stress either during growth or during post-growth cooling [7,8]. The growth of AlN transition layer (TL) following by related buffer AlxGa1−xN layers are used between Si and GaN to overcome these issues [9,10,11]. Although the use of different step graded AlGaN and AlN buffer layers have been widely studied [12,13,14,15,16,17], the nucleation of the AlN layer on Si substrate is not well understood [18].…”