Effect of hot-carrier energy relaxation on main properties of collapsing field domains in avalanching GaAs

Abstract

Electric-field-induced reversible avalanche breakdown in a GaAs microcrystal due to cross band gap impact ionization Appl.Multiple "collapsing" field domains are a physical reason for superfast switching and sub-terahertz (sub-THz) emission experimentally observed in powerfully avalanching GaAs structures. This phenomenon, however, has been studied so far without considering carrier energy relaxation and that essentially has restricted the possibility of correct interpretation of experimental results. Here, we apply a hydrodynamic approach accounting for non-local hot-carrier effects. The results confirm the collapsing domain concept, but show that the domains cannot reduce well below 100 nm in width, since a moving collapsing domain leaves behind it a tail of hot carriers, which causes broadening in the rear wall of the domain. This puts principal restrictions on the emission band achievable with our unique avalanche mm-wave source to about 1 THz. Another finding suggested here is a physical mechanism for the single collapsing domain's quasi-steady-state motion determined by powerful impact ionization. The results are of significance for physical interpretation of properties of our pulsed sub-THz source, which has recently demonstrated its application potential in mmwave imaging in both amplitude and time-domain pulse modes with picosecond time-of-flight precision. V C 2015 AIP Publishing LLC. [http://dx.

Avalanche Delay and Dynamic Triggering in GaAs-Based S-Diodes Doped With Deep Level Impurity

“…That is why, in order to reduce parasitic inductance, it is important to use new types of switches. An example of such devices are superfast GaAs switches, which are switched due to the formation of current filaments with a diameter of 20-30 μm and a current density of up to 10 MA/cm 2 [5]- [7]. The work will show that such a high current density makes it possible to develop generators of current pulses with an amplitude of up to 45 A and a duration of 1.1 ns with an optical power of 135 W.…”

“…Earlier a switching mechanism of the said device was supposedly attributed to the generation of collapsing field domains (CFDs) in an avalanche regime [8], [9]. The CFD phenomenon has been found from physics-based numerical and experimental studies of superfast switching transient in powerfully avalanching GaAs bipolar transistors [5]- [7] and claims to explain superfast switching in all GaAs devices discussed in the literature over the past 30 years. The CFD effect is actually a bipolar (in the presence of both electrons and holes) Gunn effect that occurs under extreme ionization in the domains exceeding the ionization threshold in amplitude by a factor of ∼3.…”

“…the domains shrink down to ∼50 nm [5]- [7], and then collapse. There is no analytical approach to describe this process, which makes questionable the applicability of Kroemer's criterion for the formation of CFDs threshold.…”

Особенности транспорта носителей заряда в структурах n-=SUP=-+-=/SUP=--n-=SUP=-0-=/SUP=--n-=SUP=-+-=/SUP=- с гетеропереходом GaAs/AlGaAs при сверхвысоких плотностях тока

“…В результате в сильных электрических полях с большими градиентами скорость электронов может существенно превысить насыщенную (эффект velocity overshoot) [17]. Процесс разогрева характеризуется временем энергетической релаксации, которое в проведенных расчетах было принято для электронов равным 0.5 и 0.3 пс для GaAs и AlGaAs соответственно [18][19][20][21]. Необходимо отметить, что при вычислении подвижностей и коэффициентов ударной ионизации как функции температуры носителей заряда используются параметры, играющие роль своих времен релаксации.…”

Изотипные гетероструктуры n-AlGaAs/n-GaAs, оптимизированные для эффективной межзонной излучательной рекомбинации при накачке электрическим током

“…Несмотря на микронную толщину данного слоя, поле в структуре меняется резко, при этом в DDFDM-модели скорость дрейфа напрямую зависит от напряженности поля и падает до насыщенной, как только носители попадают в область сильного электрического поля. В EBFDM-модели наблюдается эффект " velocity overshoot" [19,23,24], а насыщенная скорость зависит от температуры электронов (рис. 4), поэтому в данном приближении необходима меньшая концентрация носителей для обеспечения транспорта и напряженность поля, в частности на гетерогранице, ниже.…”