GaN-on-diamond technology platform: Bonding-free membrane manufacturing process

Abstract

GaN-on-diamond samples were demonstrated using a membrane-based technology. This was achieved by selective area Si substrate removal of areas of up to 1 cm × 1 cm from a GaN-on-Si wafer, followed by direct growth of a polycrystalline diamond using microwave plasma chemical vapor deposition on etch exposed N-polar AlN epitaxial nucleation layers. Atomic force microscopy and transmission electron microscopy were used to confirm the formation of high quality, void-free AlN/diamond interfaces. The bond between the III-nitride layers and the diamond was validated by strain measurements of the GaN buffer layer. Demonstration of this technology platform is an important step forward for the creation of next generation high power electronic devices.

Thermal stress modelling of diamond on GaN/III-Nitride membranes

“…This value is lower than the reported tensile strength of GaN (4 to 7.5 GPa at room temperature) and similar to those reported in previous studies [17,34].…”

“…Previous reports have shown diamond on GaN/III-N membranes from 0.5 to 5 mm in diameter under stresses of around 0.7 GPa due to the thermal cycling [17]. The stress is lower than the experimentally reported mechanical strength of GaN (compressive strength of 10 to 15 GPa and tensile strength of 4 to 7.5 GPa) [32,33,34] and far less than density functional theory (DFT) estimates of the tensile strength (30 to 40 GPa) [35,36].…”

“…The wafer stack has been modelled in the COMSOL Multiphysics® FEM package using the plasma [17,48]. Also, smaller samples minimise any diamond thickness variation over the sample owing to the small plasma size at these conditions.…”

“…GaN-on-diamond is not trivial to fabricate, but can be realised either by surface activated wafer bonding [10,11,12,13,14] or heteroepitaxial growth. Growth of GaN onto diamond [15] [16,17,6,18,19]. In the wafer bonding approach, it is imperative to achieve a sub-nanometre surface roughness in order for Van der Waals bonding to occur.…”

“…1. This can be achieved using an inductively coupled plasma (ICP) [17]. This membrane technique has been realised for other GaN applications including light emitting diodes, planar photonic devices [26,27,28] and impedance based sensors [29,30,31].…”