Experimental assessment of anomalous low-frequency noise increase at the onset of Gunn oscillations in InGaAs planar diodes

Abstract

In this work, the presence of anomalous low-frequency fluctuations during the initiation of higher frequency oscillations in InGaAs-based Gunn planar diodes has been evidenced and investigated. Accurate measurements showing the evolution of the power spectral density of the device with respect to the applied voltage have been carried out. Such spectra have been obtained in the wide frequency range between 10 MHz and 43.5 GHz, simultaneously covering both the low-frequency noise and the fundamental oscillation peak at some tens of GHz. This provides valuable information to better understand how these fluctuations appear and how these are distributed in frequency. For much higher frequency operation, such understanding can be utilized as a simple tool to predict the presence of Gunn oscillations without requiring a direct detection.

Comprehensive characterization of Gunn oscillations in In0.53Ga0.47As planar diodes

“…Previous works have predicted and evidenced experimentally an anomalous increase of the noise at lower frequencies at the onset of higher-frequency Gunn or other type of oscillations [30][31][32][33], which then vanishes once the oscillations are stable. This effect can be used as an indicator to anticipate the presence of very-high-frequency GOs in cases in which the lack of adequate equipment or lowpower levels makes difficult a proper direct detection.…”

Anisotropic Hot-Electron Kinetics Revealed by Terahertz Fluctuation

“…In this work, we not only experimentally demonstrate the direct evidence of T e ≫ T L , a hallmark of the far-from-thermal-equilibrium nature of current-carrying GaAs nanodevices, but also demonstrate that T e and T L show distinctive spatial patterns: while SThM measurements show smooth and structureless T L -profile, the T e -profile imaged by SNoiM is found to exhibit unexpected remarkable expansion of hotspots. Distinct anisotropy is found in the formation of the hot-electron domain (HED), which is interpreted as due to the electron transfer to the upper L-valleys. − The effect reported in this work is distinguished from the well-known dynamic high-field domain (HFD) formation in the Gunn effect − in that the induced HED is stationary and invokes a local self-enhancing nonlinear effect while globally maintaining quasi-linear transport characteristics. Our experimental finding demonstrates the decisive importance of employing our new passive terahertz imaging to map T e nanoprofiles in addition to conventional T L -profiles for a deeper understanding of nonequilibrium electron kinetics in a broad range of nanomaterials/nanodevices beyond the conventional concept of Joule heating. ,− …”

Two‐terminal InGaAs microwave amplifier

“…The planar Gunn amplifiers were fabricated on InGaAs channel layer grown by molecular-beam epitaxy (MBE) on InP wafer including a 300 nm In 0.52 Al 0.48 As buffer layer, a 300-nm InGaAs channel layer, and a 200-nm InGaAs cap layer. The doping density (N D ) of the channel layer is 8 3 10 16 cm 23 to make sure N D L C > 10 12 cm 22 [22]. The cap layer was doped at 2 3 10 18 cm 23 .…”