Optoelectron. Semicond. Tech. 57, 93-100 (2022)

Ya. M. Olikh, M. D. Tymochko


We have conducted the temperature and amplitude dependencies of the charge carriers concentration and its mobility analysis in GaN/Al0,2Ga0,8N/GaN/AlN on sapphire structures growing MOCVD method under the ultrasonic loading (longitudinal waves, fUS = 9 MHz). We found out the temperature peculiarities of electronic characteristics changes, it is allowed us to consider our system as complex with parallel conduction channels. In order to study the effect of ultrasound loading separately on both the flow of 3DEG and 2DEG charge carriers, a mathematical operation of separating these flows was carried out. It is shown, that at high temperatures (Т ˃ 200 K), 3DEG conductivity prevails, which has a thermal activation character and is described by the acoustically induced transformation of the metastable DX center. At temperatures (T ˂ 150K), 2DEG conductivity prevails. Thus, AlGaN/GaN and GaN/AlGaN boundaries can exhibit 2DEG conductivity (σ2D), while film layers (GaN buffer and AlGaN barrier layer are 3DEG conductivity (σ3D)). In the AlxGa1-xN structures containing DX centers, under US loading, there is a periodic change in the distance between the positions of the donor atom. Here, the determining mechanism is tunneling, the nature of which is related with dislocations. The horizontal sections observed in the experiment arise as a result of the tunnel emission of charge carriers through the quasi-resonant level. It was established that 3DEG and 2DEG charge carriers differ in the nature of temperature changes in concentration (with increasing temperature, there is an increase in 3DEG concentration and independence from temperature in 2DEG concentration) and mobility (decrease in 3DEG, but increase in 2DEG). It is shown that the influence of ultrasound in both cases, both for 3DEG and for 2DEG, of charge carriers is qualitatively similar - there is an increase in the 3DEG and 2DEG carriers concentration and a decrease in the absolute values of 3DEG and 2DEG mobility. Acoustically induced changes in electrical parameters most likely occur near dislocations that actively interact with ultrasonic waves.

Keywords: ultrasound, gallium-nitride, electron transport, metastable centers, Hall effect


1. L. Dong, J.V. Mantese, V. Avrutin, Ü. Özgür, H. Morkoç, and S.P. Alpay. Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple quantum wells. J. Appl. Phys. 2013. 114. P. 043715.

2. Nitin Goyala, and Tor A. Fjeldly. Effects of strain relaxation on bare surface barrier height and two-dimensional electron gas in AlxGa1-xN/GaN. J. Appl. Phys. 2013.113. P. 014505.

3. Ya.M. Olikh, M.D. Tymochko, V.V. Kaliuzhnyi, O.Ye. Bieliaiev. Osoblyvosti akustoindukovanykh zmin elektrofizychnykh kharakterystyk u heterostrukturakh GaN/Al0,2Ga0,8N/GaN/AlN. Optoelektronika ta napivprovidnykova tekhnika. 2020. 55. S. 109-116.

4. V.V. Kaliuzhnyi, O.I. Liubchenko, M.D. Tymochko, Y.M. Olikh, V.P. Kladko, A.E. Belyaev. Investigation of traps in AlGaN/GaN heterostructures by ultrasonic vibrations. Ukr. J. Phys. 2021. 66, №12. P. 1058-1062.

5. T.R. Lenka, A.K. Panda. Characteristics study of 2DEG transport properties of AlGaN/GaN and AlGaAs/GaAs-based HEMT. Semiconductors. 2011. 45, №5. P.650-656.

6. J. Smart, J. R. Shealy, N. G. Weimann, K. Chu, M. Murphy, W. J. Schaff, and L. F. Eastman. Scattering mechanisms limiting two-dimensional electron gas mobility in Al0.25Ga0.75N/GaN modulation-doped field-effect transistors J. Appl. Phys. 2000.87. P. 3900.

7. O. Ambacher, J.Smart, J. R.Shealy, et al. Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N- and Ga-face AlGaN/GaN heterostructures. J. Appl. Phys.1999. 85. P. 3222-3233.

8. E. Frayssinet, W. Knap, P. Lorenzini, et al. High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates. Appl. Phys. Lett. 2000. 77, №16. P. 2551.

9. I. A. Buyanova, A. U. Savchuk, M. K. Sheinkman, M. Kittler. Influence of subthreshold ultrasound treatment on the recombination properties of dislocations in GexSi1-x-Si heterostructures, Semicond. Sci. Technol. 1994. 9, №11. P. 2042-2046.

10. Ia.M. Olikh, M.D. Tymochko, V.P. Kladko, O.I. Liubchenko, O.Ie. Bieliaiev, V.V. Kaliuzhnyi. Znachennia DX-tsentriv dlia akustoindukovanykh protsesiv perebudovy defektiv v GaN/AlGaN. Optoelektronika ta napivprovidnykova tekhnika. 2021. 56. S. 61-70.

11. D.Y. Protasov, T.V. Malin, A.V. Tikhonov, et al. Electron scattering in AlGaN/GaNheterostructures with a two-dimensional electron gas. Semiconductors.2013. 47. Р. 33-44.

12. K. Alfaramawi. Dislocation scattering-limited electron mobility in wurtzite n-type gallium nitride. Journal of Ovonic Research. 2018. 12, №3. P.147-154.

13. A.E. Beliaev, N.S. Boltovets, V.N. Yvanov, V.P. Kladko, R.V. Konakova, Ya.Ia. Kudryk, A.V. Kuchuk, V.V. Mylenyn, Yu.N. Sveshnykov. O mekhanizme tokoperenosa, obuslovlennom dyslokatsyiamy v nitrid-hallievykh diodakh Shottky. FTP. 2008. 42, №6. P.706-710.

14. Ya.M. Olikh, M.D. Tymochko, O.Ya.Olikh, and V.A. Shenderovsky. Clusters of Point Defects Near Dislocations as a Tool to Control CdZnTe Electrical Parameters by Ultrasound. Journal of Electronic Materials. 2018. 47, №8. Р. 4370-4378.

15. R. Zeisel, M.W. Bayerl, S.T.B. Goennenwein, et al. DX-behavior of Si in AlN. Phys. Rev. B. 2000. 61. P. R16283.

16. G.S. Cargill, A. Segmueller, T.F. Kuech, and T.N. Theis. Lattice strain from DX centers and persistent photocarriers in Sn-doped and Si-doped Ga1-xAlxAs. Phys. Rev. B. 1992. 46. P.10078-10085.

Я. М. Оліх, М. Д. Тимочко


Проведено аналіз температурних та амплітудних залежностей концентрації носіїв заряду та їхньої рухливості в MOCVD гетероструктурах GaN/Al0,2Ga0,8N/GaN/AlN на сапфірі в умовах акустичного навантаження (поздовжні хвилі, f ~ 9 МГц). Виявлені температурні особливості змін електрофізичних характеристик дозволили розглядати нашу систему як складну – з паралельними каналами провідності. Показано, що при високих температурах (Т ˃ 200 К) переважає 3DEG провідність, яка має термоактиваційний характер і описується акустоіндукованою перебудовою метастабільного DX–центра. За температур (Т ˂ 150К) переважає 2DEG провідність. Тут визначальним механізмом є тунельний, природа якого пов'язана з дислокаціями. Акустоіндуковані зміни електрофізичних параметрів, найімовірніше, відбуваються поблизу дислокацій, які активно взаємодіють з ультразвуковими хвилями.

 Ключові слова: ультразвук, гетероструктури GaN/AlGaN/GaN/AlN, електронний транспорт, метаста­більні центри, ефект Холла