研究目的
To compare the mechanisms of the appearance of current oscillations in diodes based on 6-, 18-, 30-, 70-, and 120-period GaAs/AlAs superlattices with a high doping level and to determine the dependence of the average drift-electron velocity on the field voltage in the diodes.
研究成果
The study concludes that the method for exclusion of the contact resistance has a low error and is effective for diodes based on a 6-period SL. The quasi-ballistic motion in conjunction with band 'destruction' ('breaking') gives a considerably larger negative differential conductivity. A reduction in the number of periods in the SL may suppress domain formation, opening up possibilities to construct generators based on Bloch oscillations.
研究不足
The study is limited by the influence of the contact resistance on the form of the I–V characteristics, especially for diodes with a small number of SL periods. The quasi-ballistic character of electron motion in SLs with a small number of periods may also limit the applicability of the findings to SLs with a larger number of periods.
1：Experimental Design and Method Selection:
The study involved comparing the mechanisms of current oscillations in diodes based on GaAs/AlAs superlattices with different numbers of periods. The theoretical models and algorithms employed included the single-particle Monte Carlo method and quasi-hydrodynamic model for calculating electron transport.
2：Sample Selection and Data Sources:
Diodes fabricated based on 6-, 18-, 30-, 70-, and 120-period GaAs/AlAs superlattices were studied. The current–voltage (I–V) characteristics of 15–30 samples of each type were measured.
3：List of Experimental Equipment and Materials:
The diodes were arranged in a waveguide chamber for THz measurements. The frequency and power of the generated THz signal were determined using a Fourier spectrometer with a detector based on a cryogenic bolometer.
4：Experimental Procedures and Operational Workflow:
The I–V characteristics of the diodes were measured and normalized to values of voltages and currents at the maximum. The resistivity of one SL period was determined, and the resistance of contacts for each experimental diode was calculated.
5：Data Analysis Methods:
The approach for analyzing experimental data included recalculation of the diode I–V characteristics to evaluate the electron velocity in the SL and comparison of the diode operation modes using an analog of the Kremer criterion.
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