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Gated modulation-type radiometric technique for microwave noise measurement is upgraded for convenient investigation of hot-electron energy relaxation and hot-phonon dynamics in a channel with a high-density electron gas. The technique is applied to a GaN-based structure held at 80 and 293 K channel temperature. The results are discussed in terms of hot-phonon effect on hot-electron energy relaxation. The hot-phonon lifetime, estimated from the noise analysis, is compared with the values obtained by more traditional techniques.

Section: Samplementioning

confidence: 99%

Microwave noise technique for measurement of hot-electron energy relaxation time and hot-phonon lifetime

Šermukšnis¹

2007

“…2. The profile was considered to be similar to that calculated for the same type heterostructure [7]. A strong (of the order of tens of kv/cm) electric field parallel to the heterointerfaces was applied to the samples.…”

Section: Sample Characterizationmentioning

confidence: 99%

Relaxation of conductivity in AlGaN/AlN/GaN two-dimensional electron gas at high electric fields

Ardaravičius¹

2007

AlGaN / AlN / GaN heterostucture with a very thin (0.6 nm) AlN spacer was investigated by conductivity relaxation measurements after a strong electric field action. To obtain the two-dimensional electron gas (2DEG) channel transport properties at high electric fields the relaxation results were extrapolated to the time of the peak of an applied nanosecond high-voltage electric pulse. Significant decrease of hot electron sheet density at high electric fields was revealed. The measured sample conductivity relaxation is decided not only by the changes of 2DEG channel conductivity due to variation of sheet density. This does not allow one to obtain corrected drift velocity values at high electric fields. The obtained results show that the AlN thickness must be more than 0.6 nm.

“…Hot phonons complicate the problem further on: the LOphonon distribution differs from the equilibrium one. Fortunately, at a high density of electron gas present in a 2D channel, the hot-electron temperature approximation holds [23,24]. Moreover, a quasi-equilibrium hot subsystem forms because of intense electron-LOphonon scattering [19].…”

Section: Fluctuation Techniquementioning

confidence: 99%

Fluctuation technique for investigation of ultrafast processes

Matulionis¹

2007

Self Cite

Microwave fluctuations contain information on hot-electron energy relaxation, intervalley transfer, real-space transfer, and other ultrafast electronic processes in semiconductors and semiconductor structures. Based on this, the novel fluctuation technique was developed for investigation of ultrafast hot-phonon effects in two-dimensional (2D) and three-dimensional (3D) channels of importance for high-speed electronics. The hot-phonon lifetime (deduced from the hot-electron fluctuations) is in good agreement with the a posteriori reported data obtained through femtosecond-laser pump-probe experiments. Moreover, the fluctuation technique demonstrates the unique experimental possibility to study the lifetime as a function of the electron temperature in a voltage-biased 2D channel, while neither Raman photon scattering nor phonon-assisted inter-sub-band absorption has provided data of this sort as yet.