Resonant Tunneling Diodes for Sub-Terahertz and Terahertz Oscillators

Abstract

Resonant tunneling diodes (RTDs) have the potential for use as compact and coherent terahertz (THz) sources operating at room temperature. In this paper, sub-THz and THz oscillators with RTDs integrated on planar circuits are described. Fundamental oscillation up to 0.65 THz and harmonic oscillation up to 1.02 THz were obtained at room temperature in our recent study. Limiting factors for oscillation frequency and output power are theoretically analyzed including tunneling and transit-time effects and parasitic elements. Oscillation frequency and its dependence on RTD size are in good agreement with the measured results. Based on this result, it is shown that fundamental oscillation up to 2.3 THz and an output power of 60 mW at 1 THz are theoretically expected by improving the structures of the RTD and the antenna. Voltage-controlled oscillation, which is useful for the precise control of frequency, is observed in the RTD oscillators. Coherent power combining in an array configuration to achieve high output power as well as mutual injection locking between the array elements are also described.

Measurements of temperature characteristics and estimation of terahertz negative differential conductance in resonant-tunneling-diode oscillators

“…In addition to the conventional inductance and capacitance, RTDs include the delay-time capacitance, which depends on the NDC at DC and the electron delay time. 26 The results of the oscillation frequency less sensitive to temperature implies that the delay-time capacitance is almost insensitive to temperature, or that the fraction of the delay-time capacitance included in the total capacitance is small. The former further implies that the electron delay time is almost insensitive to temperature, because the NDC at DC is concluded to be insensitive to temperature, as discussed above.…”

“…6, where G RTD and C RTD are the NDC and capacitance of RTD, respectively, G rad is the radiation conductance of the antenna, G loss is the conductance due to the Ohmic loss of the antenna electrode, and jB ant is the susceptance of the antenna. G RTD is written as 26 G RTD =a (3/4) bv ac 2 , which is obtained by the expansion of the I-V curve up to the third order of the voltage measured from the center of the NDC region. a and bv ac 2 are the linear and nonlinear terms of the absolute value of the NDC, respectively, and v ac is the amplitude of the oscillation voltage across -G RTD .…”

Terahertz oscillation of resonant tunneling diodes with deep and thin quantum wells

“…On the electron device side, oscillators with heterostructure bipolar transistors (HBTs), high electron mobility transistors (HEMTs), and Si CMOS transistors are being studied intensively as THz sources [9,10,11,12]. Resonant tunneling diodes (RTDs) are also a good candidate [13,14,15]. High-frequency and high-power oscillation has been achieved at room temperature [16,17,18,19,20,21].…”

Room-temperature two-color lasing by current injection into a GaAs/AlGaAs coupled multilayer cavity fabricated by wafer bonding

“…[3][4][5] Several types of continuous-wave THz emitters have also been studied and developed using semiconductor technologies. For example, quantum cascade lasers (QCLs), [6][7][8] resonant tunneling diodes (RTDs), 9,10) and photomixers 11,12) have been reported so far. Recently, intracavity difference-frequency generation (DFG) in dual-wavelength mid-infrared QCLs has been demonstrated as a THz source.…”