Mohamadali is an experienced Postdoctoral researcher at Stanford University with a demonstrated history of working in high-power high-frequency transistors, all-diamond diodes, and diamond integration for thermal management, III-V wide bandgap semiconductors, integrated microsystems including MEMS/NEMS devices, and microfluidic channels. He is an expert in fab process design-integration, process and device modeling (Athena, Atlas), thin-film deposition techniques (Evaporation, Sputtering, PVD, ALD, and PECVD), dry etching (ICP/RIE etching of Diamond, AlN, SiN, Al2O3, SiO2), wet etching (bulk Si micromachining), and single-crystalline/polycrystalline diamond growth. He is currently working on the growth, fabrication, and characteristics of GaN HEMTs with diamond integrated for thermal management to solve the self-heating problem of mm-wave devices.
Srabanti Chowdhury, Postdoctoral Faculty Sponsor
- Impact of Diamond Passivation on f(T) and f(max) of mm-wave N-Polar GaN HEMTs IEEE TRANSACTIONS ON ELECTRON DEVICES 2022
- Low Thermal Budget Growth of Near-Isotropic Diamond Grains for Heat Spreading in Semiconductor Devices ADVANCED FUNCTIONAL MATERIALS 2022
- Current Transient Spectroscopic Study of Vacancy Complexes in Diamond Schottky p-i-n Diode IEEE TRANSACTIONS ON ELECTRON DEVICES 2022
- A study on sub-bandgap photoexcitation in nitrogen- and boron-doped diamond with interdigitated device structure APPLIED PHYSICS LETTERS 2022; 120 (11)
Record-Low Thermal Boundary Resistance between Diamond and GaN-on-SiC for Enabling Radiofrequency Device Cooling.
ACS applied materials & interfaces
The implementation of 5G-and-beyond networks requires faster, high-performance, and power-efficient semiconductor devices, which are only possible with materials that can support higher frequencies. Gallium nitride (GaN) power amplifiers are essential for 5G-and-beyond technologies since they provide the desired combination of high frequency and high power. These applications along with terrestrial hub and backhaul communications at high power output can present severe heat removal challenges. The cooling of GaN devices with diamond as the heat spreader has gained significant momentum since device self-heating limits GaN's performance. However, one of the significant challenges in integrating polycrystalline diamond on GaN devices is maintaining the device performance while achieving a low diamond/GaN channel thermal boundary resistance. In this study, we achieved a record-low thermal boundary resistance of around 3.1 ± 0.7 m2 K/GW at the diamond/Si3N4/GaN interface, which is the closest to theoretical prediction to date. The diamond was integrated within 1 nm of the GaN channel layer without degrading the channel's electrical behavior. Furthermore, we successfully minimized the residual stress in the diamond layer, enabling more isotropic polycrystalline diamond growth on GaN with thicknesses >2 mum and a 1.9 mum lateral grain size. More isotropic grains can spread the heat in both vertical and lateral directions efficiently. Using transient thermoreflectance, the thermal conductivity of the grains was measured to be 638 ± 48 W/m K, which when combined with the record-low thermal boundary resistance makes it a leading-edge achievement.
View details for DOI 10.1021/acsami.1c13833
View details for PubMedID 34875169
- Demonstration of Monolithic Polycrystalline Diamond-GaN Complementary FET Technology for High-Temperature Applications ACS APPLIED ELECTRONIC MATERIALS 2021; 3 (10): 4418-4423
- Diamond-Incorporated Flip-Chip Integration for Thermal Management of GaN and Ultra-Wide Bandgap RF Power Amplifiers IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY 2021; 11 (8): 1177-1186
- Development of Polycrystalline Diamond Compatible with the Latest N-Polar GaN mm-Wave Technology CRYSTAL GROWTH & DESIGN 2021; 21 (5): 2624-2632
- Polycrystalline diamond growth on beta-Ga2O3 for thermal management APPLIED PHYSICS EXPRESS 2021; 14 (5)
- Diamond Integration on GaN for Channel Temperature Reduction IEEE. 2021: 70-74
- Analysis of mobility-limiting mechanisms of the two-dimensional hole gas on hydrogen-terminated diamond PHYSICAL REVIEW B 2020; 102 (7)
- Schottky Barrier Height Analysis of Diamond SPIND Using High Temperature Operation up to 873 K IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY 2020; 8: 614–18
Hydrogen-terminated diamond FET and GaN HEMT delivering CMOS inverter operation at high-temperature
View details for Web of Science ID 000615719100010
- A Study on the First-Derivative Output Properties of GaN Static Induction Transistor with Submicrometer Fin Width PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2019
- A Study on the Growth Window of Polycrystalline Diamond on Si3N4-coated N-Polar GaN CRYSTALS 2019; 9 (10)