Characterization of high-quality MBE-grown GaN films on intermediate-temperature buffer layers

Journal of Applied Physics

et al. 2003

We report the growth of high-mobility Si-doped GaN epilayers utilizing unique double buffer layer ͑DBL͒ structures, which consist of a thin buffer layer and a thick GaN intermediate-temperature buffer layer ͑ITBL͒. In this study, three types of DBL were investigated: ͑i͒ thin GaN low-temperature buffer layer /GaN ITBL ͑type I͒; ͑ii͒ nitridated Ga metal film/GaN ITBL ͑type II͒; and ͑iii͒ thin AlN high-temperature buffer layer /GaN ITBL ͑type III͒. Systematic measurements were conducted on the electron mobilities and the low-frequency noise over a wide range of temperatures. It is found that the electron mobilities of the GaN films are substantially improved with the use of DBLs, with the sample using type III DBL which exhibits the highest low-temperature mobility. Furthermore, the same sample also demonstrates the elimination of deep levels at 91 and 255 meV below the conduction band. This is believed to result from the relaxation of tensile stress during growth with the use of type III DBLs.

Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of low-frequency noise in molecular beam epitaxy-grown GaN epilayers deposited on double buffer layers

Journal of Applied Physics

et al. 2003

“…The capture cross section of the deep-level is found to be 1 × 10 −14 cm 2 . Previous works on photoluminescence and photoreflectance spectroscopies showed that ITBL can effectively reduce the tensile stress leading to the lowering of the energy barrier for surface diffusion of Ga during heteroepitaxial growth [1,5,15]. This is believed to result in the observed reduction in the trap density and superior hot-electron hardness in device A.…”

Section: Resultsmentioning

confidence: 83%

“…The authors had recently reported on MBE growth of high-quality N-faced GaN layers on novel double buffer layer structures, which consist of a thin conventional GaN LTBL and a thick GaN intermediate-temperature buffer layer (ITBL) deposited at 500 °C and 690 °C respectively [1,5,6]. In this paper we report systematic characterizations of simple metal-semiconductor-metal (MSM) structures fabricated on Ga-faced GaN thin films by low-frequency noise and deep-level transient Fourier spectroscopy (DLTFS) measurements.…”

mentioning

confidence: 99%

Low‐frequency noise characterizations on Ni/GaN Schottky diodes deposited on intermediate‐temperature buffer layers

Surya

et al. 2003

phys. stat. sol. (c)

Self Cite

Silicon dioxide passivated back-to-back Schottky diodes were fabricated by depositing Ni on rf plasmaassisted molecular beam epitaxy-grown GaN utilizing a unique double buffer layer structure. In this study, both low-frequency noise and deep-level transient Fourier spectroscopy (DLTFS) measurements were conducted to characterize the effects of intermediate-temperature buffer layers (ITBLs) on the hotelectron hardness of GaN Schottky diodes. Device A was fabricated with a double buffer layer consisting of a thin AlN high-temperature buffer layer (HTBL) and a GaN ITBL. Device B consists of a single AlN HTBL. Low-frequency noise results measured from the as-deposited devices show a significant reduction in the noise level, over an order of magnitude, for device A indicative of the substantial reduction in the trap density in the GaN thin films deposited on ITBLs. Hot-electron hardness of the devices was examined through the application of high voltage stress. The increase in the low-frequency noise for device A after voltage stressing is much smaller and no detectable deep-level is observed by both low-frequency noise and DLTFS techniques. However, both characterization techniques indicate a generation of a deeplevel at 780 meV below the conduction band edge for device B. Based on detailed optical and electrical characterizations of the samples, the improved device properties for device A are attributed to the relaxation of residue strain in the epilayer during growth due to the utilization of ITBL [W. K. Fong et al.,

Study of Low-Frequency Excess Noise Transport in Ga-Face and N-Face GaN Thin Films Grown on Intermediate-Temperature Buffer Layer by RF-MBE

Xie

et al. 2002

phys. stat. sol. (a)

Self Cite

We report detailed investigations of low‐frequency excess noise in both Ga‐faced and N‐faced GaN thin films grown by RF‐plasma molecular beam epitaxy. The GaN epilayers were grown on double buffer layers, and consisted of a thick intermediate‐temperature buffer layer (ITBL) deposited at 690 °C and a conventional thin buffer layer. Deposition of the thin buffer layer is used to control the polarity of the GaN epilayer. Low‐frequency excess noise was studied in detail to examine the effects on the ITBL on the noise. The low‐frequency noise is attributed to the correlated fluctuations in number and mobility of carriers, arising from the capture and emission by localized states. Our experimental results show that the polarity of the GaN epilayer and the utilization of ITBL have strong influence on the defect density of the GaN material.