Hot-electron energy relaxation time in Ga-doped ZnO films

Šermukšnis, E.; Liberis, J.; Ramonas, M.; Matulionis, A.; Toporkov, Mykyta; Liu, H. Y.; Avrutin, Vitaliy; Özgür, Ü.; Morkoç̌, H.

doi:10.1063/1.4907907

Cited by 26 publications

(25 citation statements)

References 45 publications

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“…Hence, we take the impact generation coefficient of ZnO as a reasonable approximation for MgZnO: , where A = 7 × 10 5 cm −1 , B = 5 × 10 6 V / cm are the calculated parameters of wide-gap ZnO 73 . The saturation velocity for electron in MgZnO sample is ~2 × 10 7 cm/s 74 and the relaxation time is assumed to be 1.5 ps 64 .…”

Section: Methodsmentioning

confidence: 99%

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Suja

Bashar

Debnath

et al. 2017

Sci Rep

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Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this paper, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29~33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

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Section: Methodsmentioning

confidence: 99%

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Suja

Bashar

Debnath

et al. 2017

Sci Rep

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“…We used three different set-ups for measurement of the noise temperature in the frequency bands from 0.2 GHz to 2.5 GHz [22], in the X band in the vicinity of 10 GHz [21]), and in the vicinity of 38.5 GHz of the Ka band [23]. The sample is either mounted into the waveguide or accessed in an on-wafer mode.…”

Section: Pulsed Measurement Of Noise Temperaturementioning

confidence: 99%

“…The set-up for (0.2 -2.5) GHz band is described in Ref. [22]. The pulse voltage generator is connected to the DUT (Fig.…”

Section: Pulsed Measurement Of Noise Temperaturementioning

confidence: 99%

“…The measurements include four steps used to obtain the noise temperature and the sample reflection coefficient, for details see Ref. [22]. The thermal walkout is controlled through measurements before, during, and after the voltage pulse.…”

Section: Pulsed Measurement Of Noise Temperaturementioning

confidence: 99%

“…We suppose that the excess hot-electron temperature T e -T b approximately equals the excess noise temperature T n -T b (Figure 7). [22], bullets -worldwide results measured by photoexcitation techniques [8][9][10][11][12][13][14][15][16][17][18][19][20]. Dotted curve is semi-empirical dependence [36].…”

Section: Experimental Datamentioning

confidence: 99%

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Window for Optimal Frequency Operation and Reliability of 3DEG and 2DEG Channels for Oxide Microwave MESFETs and HFETs

Matulionis¹

2016

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Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures

Ullah

Ding

Nakagawara

et al. 2017

Physica Rapid Research Ltrs

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The BeMgZnO/ZnO heterostructures are capable of producing sufficiently high sheet electron densities to allow field effect transistor operation near or at the LO phonon plasmon resonance frequency for minimal LO phonon lifetimes and high electron velocity. Schottky barriers are imperative for the implementation of the aforementioned devices. Therefore, we have undertaken fabrication and characterization of Ag Schottky barriers on Zn-polar Be 0.02 Mg 0.26 ZnO/ZnO heterostructures, exhibiting the said two-dimensional electron gas (2DEG), grown by molecular beam epitaxy. Ag Schottky barriers are characterized by current-voltage (I-V) measurements in the temperature range from 80 to 400 K. At room temperature, the highest barrier height of 1.07 eV and an ideality factor of 1.22 are achieved with a rectification ratio of about eight orders of magnitude. Richardson constants of 38 AE 22 and 29 AE 20 A cm À2 K À2 are found using modified Richardson plots from Schottky diodes fabricated on two different structures. These values are consistent with the theoretical estimate of 36 A cm À2 K À2 for Be 0.02 Mg 0.26 ZnO. The temperature variation of barrier heights and ideality factors, an aberration from pure thermionic behavior, has been explained with plausible spatial inhomogeneity of barrier height with three Gaussian distributions in the temperature ranges of 80-200, 220-280, and 300-400 K.ZnO as a wide bandgap semiconductor [1] (%3.3 eV at room temperature) with high electron saturation velocity [2] (theoretical 3.5 Â 10 7 cm s À1 ), has garnered popularity owing to its potential for applications in thin film transparent transistors, transparent electrodes for solar cells, light emitters, chemical and biological sensors etc. [1,[3][4][5] Alloying with other II-VI oxides with higher bandgap (MgO and BeO) paves the way for heterojunction field effect transistors with polarization induced two-dimensional electron gas (2DEG). [6,7] Performance of such devices at high electric field, where electron transport is highly controlled by longitudinal optical (LO) phonons, [8] suffers due to accumulation of non-equilibrium hot LO phonons owing to strong electron-LO phonon coupling. Devices operating at or near plasmon-LO phonon resonance exhibit high electron drift velocity [9][10][11] allowed by ensuing ultrafast decay of hot LO phonons, [12,13] which leads to faster electron energy relaxation [14] and optimum device operation conditions (higher frequencies, lower degradation). [8] Plasmon-LO phonon resonance occurs when the energy of the LO phonon becomes similar to the plasmon energy, which occurs in ZnO at a bulk carrier concentration of %7 Â 10 18 cm À3 (ZnO LO phonon energy 72 meV). [14] Clearly, this is far beyond the MESFET operating window (typically 1 Â 10 17 À5 Â 10 17 cm À3 ). The necessity of high electron density makes the use of ZnO heterostructures with 2DEG imperative.Sheet carrier densities up to 8 Â 10 12 cm À2 (corresponding bulk concentration of 2 Â 10 19 cm À3 ) have been reported with MgZnO/ZnO heterostructu...

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Hot-electron energy relaxation time in Ga-doped ZnO films

Cited by 26 publications

References 45 publications

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Window for Optimal Frequency Operation and Reliability of 3DEG and 2DEG Channels for Oxide Microwave MESFETs and HFETs

Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures

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Hot-electron energy relaxation time in Ga-doped ZnO films

Cited by 26 publications

References 45 publications

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Electrically driven deep ultraviolet MgZnO lasers at room temperature

Window for Optimal Frequency Operation and Reliability of 3DEG and 2DEG Channels for Oxide Microwave MESFETs and HFETs

Characterization of Ag Schottky Barriers on Be0.02Mg0.26ZnO/ZnO Heterostructures

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Product

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Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures