Journal of Crystal Growth 237–239 (2002) 1176–1179 On the capacitance–voltage characteristics of Al/BaTiO 3 /GaN MFS structures M. Senthil Kumar*, R.R. Sumathi, N.V. Giridharan, R. Jayavel, J. Kumar Crystal Growth Centre, Anna University, Chennai 600 025, India Abstract A metal–insulator–semiconductor device structure has been successfully grown on GaN by using ferroelectric BaTiO 3 (BTO) as an insulating layer. The GaN and BTO films of the GaN metal–ferroelectric–semiconductor (MFS) structures have been characterised using high-resolution X-ray diffraction, wide-angle X-ray diffraction and energy dispersive X-ray analysis. The electrical properties of fabricated Al/BaTiO 3 /GaN MFS structures have been characterised by high- frequency capacitance–voltage (C–V) measurement. C–V characteristics are remarkably improved for GaN MFS with a ferroelectric insulator when compared to other traditional oxide insulators. The fabricated GaN MFS structures approach inversion just for the applied bias of 5 V, which is mainly due to the high dielectric constant and large polarisation field of the gate ferroelectric layer. r 2002 Elsevier Science B.V. All rights reserved. PACS: 81.05.Ea; 77.84.Dy; 82.80.Pv; 85.30.Tv Keywords: A1. X-ray diffraction; B1. Gallium compounds 1. Introduction Gallium nitride (GaN) has been the material for active research from the last decade due to the recent establishment of high efficiency blue/violet light emitting diodes (LEDs) and blue laser diodes (LDs) [1,2]. Also, GaN-based electronic devices could be operated in a high temperature environ- ment with high power conditions because of wide band-gap nature as well as high thermal conduc- tivity [3–6]. The very strong chemical bonds of GaN compounds make them very stable, which diminish the degradation problems of the fabri- cated devices. p-Type doping of GaN has now practically matured and the GaN-based LED and LD device structures are becoming well estab- lished. However, GaN technology is yet to be developed for the fabrication of practical MES- FETs and MOSFETs. The traditional GaN MIS structures are fabricated with conventional oxides like SiO 2 [7,8], Si 3 N 4 [9] and Ga 2 O 3 (Gd 2 O 3 ) [10] as insulators. GaN metal–insulator–semiconductor (MIS) devices with these conventional oxides give good inversion characteristics only under the high- applied gate voltage, which is incompatible with many other electronic devices. In the present work, BaTiO 3 ferroelectric oxide has been applied as gate material to overcome this problem because of large polarisation and high dielectric constant of ferro- electric gate material. The concept of metal–ferroelectric–semiconduc- tor (MFS) was first proposed by Wu in the 70s *Corresponding author. Tel.:/fax: +91-44-235-27-74. E-mail address: m.senthilkumar@mailcity.com (M. Senthil Kumar). 0022-0248/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0022-0248(01)02152-2