High-frequency response and the possibilities of frequency-tunable narrow-band terahertz amplification in resonant tunne
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ONIC PROPERTIES OF SOLID
HighFrequency Response and the Possibilities of FrequencyTunable NarrowBand Terahertz Amplification in Resonant Tunneling Nanostructures V. V. Kapaev*, Yu. V. Kopaev†, S. A. Savinov, and V. N. Murzin Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow, 119991 Russia *email: [email protected] Received July 6, 2012
Abstract—The characteristics of the highfrequency response of single and doublewell resonant tunneling structures in a dc electric field are investigated on the basis of the numerical solution of a timedependent Schrödinger equation with open boundary conditions. The frequency dependence of the real part of high frequency conductivity (highfrequency response) in In0.53Ga0.47As/AlAs/InP structures is analyzed in detail for various values of the dc voltage Vdc in the negative differential resistance (NDR) region. It is shown that doublewell threebarrier structures are promising for the design of terahertzband oscillators. The presence of two resonant states with close energies in such structures leads to a resonant (in frequency) response whose frequency is determined by the energy difference between these levels and can be controlled by varying the parameters of the structure. It is shown that, in principle, such structures admit narrowband amplification, tuning of the amplification frequency, and a fine control of the amplification (oscillation) frequency in a wide range of terahertz frequencies by varying a dc electric voltage applied to the structure. Starting from a certain width of the central intermediate barrier in doublewell structures, one can observe a collapse of resonances, where the structure behaves like a singlewell system. This phenomenon imposes a lower limit on the oscilla tion frequency in threebarrier resonant tunneling structures. DOI: 10.1134/S1063776113030096 †
1. INTRODUCTION
The development of the physical principles of amplification, generation, and conversion of subtera hertz and terahertzband electromagnetic waves is one of the problems that determine the progress in modern solidstate electronics towards high frequen cies and superfast responses. The operation frequen cies of common fieldeffect transistors, impact ava lanche transittime diodes, and Gunn oscillators are restricted to about hundreds of gigahertz. Resonant tunneling diodes (RTDs), which are characterized by extremely small times of transient electronic processes (less than 1 ps), comparable with those of the best superconducting devices, are free of this restriction [1]. It is RTDs in which recordbreaking response time was obtained and oscillation in the terahertz band was achieved with the use of both closedtype resona tors [2] and microstriptype resonator antennas [3–7], which are more efficient in this frequency band. These results show that oscillators based on RTD elements are promising for the generation of terahertzband radiation, especially in view of the monolithic integra tion of such elements in a single microchi
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