Diamond-coated three-dimensional GaN micromembranes: Effect of nucleation and deposition techniques

Abstract

In this work, we present technological issues in the deposition of polycrystalline diamond films as a backside heat spreader for GaN membranes. We compared three nucleation techniques, including standard ultrasonic seeding by diamond powder (DP) in deionized water, drop-off technique with DP in solution and polymer based nucleation by polyvinyl alcohol (PVA) polymer composite containing fine grained DP. The diamond growth was performed in a hot filament or microwave plasma chemical vapor deposition system. We found that standard nucleation techniques (ultrasonic seeding or immersing in diamond powder solution) resulted in damaging or cracking of GaN membranes, or low nucleation efficiency in the Z-depth of the structures. Implementation of a novel nucleation technique with PVA polymer composite containing diamond powder led to coating of both bottom and top parts of the membrane including side walls. The coverage homogeneity was evaluated by scanning electron microscopy and Raman spectroscopy. The obtained results indicate that the efficiency (and/or nucleation density) of the polymer-based technique is comparable with standard ultrasonic seeding and could be used in preference for nucleation of soft and fragile substrates.

Polymer‐based nucleation for chemical vapour deposition of diamond

“…This surface morphology is similar to the reference sample nucleated using ultrasonic seeding with diamond nanoparticles [Figure (e)]. The nucleation method based on the PVA composites with diamond nanoparticles has been already successfully utilized for diamond growth on a fragile 3D GaN membranes …”

Direct Deposition of CVD Diamond Layers on Top of GaN Membranes

“…The diamond deposition on the GaN membranes with diameters of 1 mm was performed in an ellipsoidal cavity microwave plasma chemical vapor deposition (CVD) reactor [2]. After diamond deposition, the membrane area was not smooth, and many wrinkles were observed.…”

“…In our previous experiments, we studied back-side diamond deposition on GaN membranes. In that study, several technological issues are highlighted, such as the importance of the polymer-based nucleation method [2]. In the present study, we show and discuss the technological issues related to front-side diamond deposition on GaN membranes (i.e., diamond growth on top of the GaN membranes), and we propose technological steps to overcome problems related to the recent procedure.…”

DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond–GaN Interfaces

“…Inasmuch as the proposed reconstruction patterns involve the topmost GaN substrate's layer, natural candidates for substitutional atoms are Si and C. The GaN material utilized in HEMTs is usually epitaxially grown on Si(111) or silicon carbide substrate layers [5,41]. These layers are either mechanically removed or chemically etched in GaN-on-diamond bonding technology [5,[20][21][22].…”