IEEE ELECTRON DEVICE LETTERS, VOL. 23, NO. 7, JULY 2002 377 A Novel Frequency-Multiplication Device Based on Three-Terminal Ballistic Junction I. Shorubalko, H. Q. Xu, I. Maximov, D. Nilsson, P. Omling, L. Samuelson, and W. Seifert Abstract—In this letter, a novel frequency-multiplication device based on a three-terminal ballistic junction is proposed and demonstrated. A 100 nm-size, three-terminal ballistic junction and a one-dimensional (1-D), lateral-field-effect transistor with trench gate-channel insulation are fabricated from high-electron-mobility GaInAs/InP quantum-well material as a single device. The devices show frequency doubling and gain at room temperature. The performance of these devices up to room temperature originates from the nature of the device functionality and the fact that the three-terminal device extensions are maintained below the carrier mean-free path. Furthermore, it is expected that the device performance can be extended up to THz-range. Index Terms—Ballistic devices, frequency-multiplication, three- terminal ballistic junctions. I. INTRODUCTION B ALLISTIC [1] devices have received increasing attention for their nonlinear electrical properties [2]–[8], which are interesting from the points of view of physics and applications. One example of ballistic devices is the ballistic rectifier [3], in which electrons are guided by a symmetry-breaking scatterer in the ballistic regime. Recently, novel nonlinear electrical properties of three-terminal ballistic junctions (TBJs) have been theoretically predicted [4] and experimentally observed [5]–[7]. Interestingly, experiments on carbon nanotubes Y-junctions showed nonlinear electrical properties [8], [9], which could be explained using similar model as used in TBJs. The main feature of these novel properties is that if finite voltages and are applied to the left and right branches of a symmetric TBJ in push-pull fashion, i.e., with , the voltage at the central branch will always be negative. This is because of chemical potential redistribution in the TBJs under condition that there is no current flowing through the central branch [4]. One technique to fabricate TBJs is to etch trenches in two-dimensional electron gas (2DEG) material [7]. Using the same technology it is possible to fabricate one-dimensional (1-D) lateral-field-effect transistor (lateral-FET) with trench gate-channel insulation [10], which can be used for amplifica- tion of signal output from the central branch of a TBJ. In this letter, we propose and demonstrate a novel fre- quency-multiplication device based on three-terminal ballistic Manuscript received March 14, 2002; revised May 6, 2002. This work was supported by the Swedish Research Council and the Swedish Foundation for Strategic Research, as well as by the European Commission through LTR re- search projects Q-SWITCH and NEAR. The review of this letter was arranged by Editor D. Ueda. The authors are with the Division of Solid State Physics, Lund Uni- versity, S-22100 Lund, Sweden (e-mail: Ivan.Shorubalko@ftf.lth.se; Hongqi.Xu@ftf.lth.se). Publisher Item Identifier S 0741-3106(02)06240-7. Fig. 1. (a) Schematic picture of the modulation-doped Ga In As InP heterostructure used for device fabrication, NID stands for not intentionally doped and SI for semi-insulating. (b) 4 4 m AFM image of the frequency-multiplication device based on T branch and 1-D lateral-FET. junction. The novel devices are fabricated by integrating T-junc- tion device [7] (one type of the TBJs) and 1-D lateral-FET with trench gate-channel insulation on high-electron-mobility GaInAs/InP quantum well structures. Electrical properties of these devices are measured. The measurements show that these integrated devices operate as frequency doubler with gain at room temperature. II. FABRICATION The fabrication of the devices starts from a modulation doped Ga In As InP heterostructure [see Fig. 1(a)]. The electrons in this structure are confined to the 2DEG formed in the quantum well (for details, see [11]). In dark, the 2DEG structure has the following electrical parameters, extracted from Hall measurements, at room temperature (all measurements presented in this letter are performed at room temperature and in dark): carrier density of 4.5 10 cm and mobility of 1.2 m Vs. Thus, the mean free path of the electrons in the 2DEG structure is approximately 130 nm at room temperature. Using electron beam lithography and wet chemical etching, the devices were defined on standard mesas with Au/Ge ohmic contacts (for details, see [12]). The 4 4 m atomic force microscope (AFM) image of the central part of a typical device 0741-3106/02$17.00 © 2002 IEEE