Ramp-type junction parameter control by Ga doping of PrBa2Cu3O7−δ barriers

Abstract

We analyzed the transport of charge carriers across PrBa2Cu3−xGaxO7−δ (PBCGO) barriers as a function of barrier thickness, Ga-doping level, temperature, and bias voltage. It was found that by Ga doping, the normal state resistance (Rn) of the junctions was systematically increased, while the critical current (Ic) remained constant. We argue that pair transport takes place by direct tunneling, whereas the quasiparticles have access to channels formed by one or more localized states inside the barrier. By Ga doping the IcRn products were increased, up to 8 mV at 4.2 K for junctions with 8 nm thick PrBa2Cu2.6Ga0.4O7−δ barriers.

High-Tc ramp-type Josephson junctions on MgO substrates for terahertz applications

“…Microwaves (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) GHz) and millimeter waves (101 GHz) were generated by a synthesized signal generator and a Gunn diode and were fed to ramp-type junctions using a coaxial cable and a waveguide, respectively. Terahertz wave signals were generated by a farinfrared (FIR) laser, pumped by a 38-W CO laser, yielding 40 mW on the 761.7-GHz formic acid line, 100 mW on the 1.40-THz diflorometan line, and 120 mW on the 2.52-THz methanol line.…”

“…Electric transport properties of the ramp-type junctions with PBCGO are well described by a combination of direct tunneling and resonant tunneling via localized states (L.S.) [12]. The total conductance can be written in terms of the direct tunneling component and the resonant tunneling component (1) where is largely independent of temperature and bias voltage.…”

Fabrication of high IcRn YBCO ramp junctions using Ga doped Pr-Ba-Cu-O barriers at 65 K

“…Other researchers have obtained high IcRn products using PBCO with Ga substitution for Cu [3], [4]. Ga substitution for Cu has been demonstrated to increase the resistivity of PBCO bulk material [I], and to increase Rn in ramp junctions [2]- [4]. Critical currents of the ramp junctions remained constant resulting in a higher IcRn product.…”

“…High IcRn values are important for a variety of applications including digital circuits, SQUIDS, etc. Other researchers have obtained high IcRn products using PBCO with Ga substitution for Cu [3], [4]. Ga substitution for Cu has been demonstrated to increase the resistivity of PBCO bulk material [I], and to increase Rn in ramp junctions [2]- [4].…”

Fabrication of Ramp-Edge Junctions With High ICRN Products by Using Cu-Poor Precursor

“…Various types of HTS junctions have been developed so far, including ramp-edge type junctions with an artificial barrier layer [1]- [5] and an interface engineered barrier [6]. The artificial barriers in most HTS junctions are formed by depositing a non-superconducting oxide material such as PrBaCuO [1]- [4] or a lowersuperconducting material such as Co-doped YBaCuO [5].…”