Solid State Physics Laboratory (SSPL), Delhi is involved in the growth of bulk and epitaxial materials of some of the most strategically important material for defence applications. R&D efforts over the years have led to vast experience and knowledge base in the laboratory in this niche area.

Modern devices require very sophisticated, complex hetero epi-structures, which are composed of stacks of thin layers with varied compositions, thicknesses varying from few mono layers to microns, controlled doping profiles with atomically abrupt interfaces. Efforts were put-in for indigenous development of such epi-structures for different microelectronic devices being required for various DRDO projects. Material epi-structures with such stringent requirement can only be achieved by epitaxial growth techniques like Molecular Beam Epitaxy (MBE), Metal Organic Chemical Vapor Deposition (MOCVD), etc.

The state-of-the-art facilities were created for bulk and epitaxial growth of various advanced III-V and IIVI semiconductor materials. SSPL has indigenously developed the technology for II-VI material which are strategic in nature and has led their production in the country through ToT to achieve self-reliance. Device quality heterostructures epi-material developed in the laboratory have been used for the development of various devices like IRFPA, GaAs and GaN-based HEMT/MMICs, High Power Laser Diodes, Solar cells, etc.

DRDO has accomplished significant developments in epi-material and bulk crystal growth technologies, during the past few years.

AlGaN/GaN HEMT Epitaxial Growth Technology

GaN-based High Electron Mobility Transistor (HEMT) heterostructures are required for the fabrication of high performance HEMT devices/Monolithic Microwave Integrated Circuits. A typical GaN HEMT heterostructure, consists of various epitaxial layers with strict control over composition as well as thicknesses at nanometre scale.

The desired smoothness/abruptness of various interfaces at sub-nanometre level requires atomic scale control over growth process. Metal Organic Chemical Vapour Deposition (MOCVD) was used for developing AlGaN/GaN HEMT epiwafer growth process due to its capability of scaling up for volume production and low manufacturing cost. MOCVD facility established at SSPL employs a Close-coupled Showerhead (CCS) reactor with growth capability of 3×2", 1×3" and 1×4" wafers (Fig. 1). The in-situ tools allow the real-time growth process monitoring along with complete susceptor temperature mapping.