Modulation-doped superlattice AlGaN barrier GaN/AlGaN HFETs

• Published in: Journal of crystal growth 2004-12, Vol.272 (1), p.318-321
• Main Authors: Chowdhury, Uttiya, Price, Raymond K., Wong, Michael M., Yoo, Dongwon, Zhang, Xuebing, Feng, Milton, Dupuis, Russell D.
• Format: Article
• Language: English
• Subjects: A1. Doping; A3. Low pressure metalorganic vapor phase epitaxy; Applied sciences; B1. Nitrides; B2. Semiconducting III–V materials; B3. Heterojunction semiconductor devices; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Defects and impurities: doping, implantation, distribution, concentration, etc; Electronics; Exact sciences and technology; Field effect devices; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Transistors
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2004.08.058

For nitride heterojunction field-effect transistors, the heterojunction forming the electron barrier has to be designed based on trade-offs between lattice mismatch, two-dimensional electron gas concentration, and alloy scattering. In this work, we study the use of a superlattice-based barrier which effectively increases the heterojunction barrier while reducing the lattice mismatch and alloy scattering. The structure studied consists of a five-period superlattice of 2 nm Al 0.2Ga 0.8N +2 nm Al 0.3Ga 0.7N on GaN grown using metalorganic chemical vapor deposition on a 6 H SiC conducting substrate. The barriers of the second and third period of the superlattice are Si-doped to give the effect of modulation doping. Devices fabricated from the structure exhibit a high g m of ∼299 mS/mm and an I ds max of 0.85 A/mm. To our knowledge, this is the first investigation of the use of superlattice structure for improvement of the barrier properties in a nitride HFET.