| Double-barrier, single-quantum-well, resonant tunneling diodes employing variable thickness Al{dollar}sb{lcub}0.25{rcub}{dollar}Ga{dollar}sb{lcub}0.75{rcub}{dollar}As barriers and 5 nm GaAs wells have been studied. Low doped GaAs buffer regions ({dollar}Nsb D{dollar} {dollar}approx{dollar} 5 {dollar}times{dollar} 10{dollar}sp{lcub}16{rcub}{dollar} cm{dollar}sp{lcub}-3{rcub}{dollar}) were placed next to the barriers to reduce the device capacitance and to prevent dopant migration into the barriers.; The diodes were mounted in a coplanar waveguide test circuit that was placed in a microwave test fixture employing Wiltron K Connector spark plug launchers to transition from the coplanar waveguide to coax. Small-signal reflection coefficient measurements were made on these diodes. The measurements were de-embedded using a two-tiered error correction scheme composed of the line-reflect-match and thru-reflect-line techniques.; A small-signal equivalent circuit model consisting of a resistor, {dollar}Rsb S{dollar}, in series with the parallel combination of a nonlinear conductance, G, and a capacitance, C, was used. The series resistance and shunt capacitance were found to be independent of bias voltage while the conductance was found to be related to the dc current-voltage characteristic {dollar}lbrack I(V)rbrack{dollar} of the diode by{dollar}{dollar}G = {lcub}{lcub}dIover dV{rcub}over{lcub}1-{lcub}dIover dV{rcub}Rsb S{rcub}{rcub}.{dollar}{dollar}; The large-signal behavior of the diode was investigated. The small-signal equivalent circuit model for the diode was used for the large-signal analysis by replacing the nonlinear conductance with an ac conductance, {dollar}Gsb{lcub}rm ac{rcub}{dollar} = {dollar}Isb1{dollar}/{dollar}Vsb1{dollar}, where {dollar}v(t){dollar} = {dollar}Vsb B{dollar} + {dollar}Vsb1{dollar} cos {dollar}omega t{dollar} is the instantaneous voltage across the conductance with {dollar}Vsb B{dollar} being the bias voltage and where {dollar}i(t){dollar} = {dollar}Isb0{dollar} + {dollar}Isb1{dollar} cos {dollar}omega t{dollar} + {dollar}Isb2{dollar} cos 2{dollar}omega t{dollar} + {dollar}cdots{dollar} is the Fourier series representation of the instantaneous current through the conductance as calculated from the current-voltage curve that has been corrected for the series resistance, {dollar}Rsb S{dollar}. The effects of higher harmonic voltage terms was found to be negligible.; The diode was studied as a microwave detector. When biased at the peak in the current-voltage curve, the diode provides a novel, full-wave rectification of a superimposed ac signal. The diode's performance as a detector is comparable to Schottky point contact detectors at low frequencies, while the resonant tunneling diode's performance degrades at higher frequencies because of its intrinsic parasitics. |
