Properties of AlN/GaN Heterostructures Grown at Low Growth Temperatures with Ammonia and Dimethylhydrazine

Caroline E Reilly,Nirupam Hatui,Pratik Koirala,Shuji Nakamura,Adedapo A Oni,Thomas E Mates,Stacia Keller,Steven P Denbaars

doi:10.3390/cryst11111412

Caroline E Reilly, Nirupam Hatui + Show 6 more

Open Access

https://doi.org/10.3390/cryst11111412

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Abstract

The integration of different electronic materials systems together has gained increasing interest in recent years, with the III-nitrides being a favorable choice for a variety of electronic applications. To increase flexibility in integration options, growing nitrides material directly on semi-processed wafers would be advantageous, necessitating low temperature (LT) growth schemes. In this work, the growth of AlN and GaN was conducted via metalorganic chemical vapor deposition (MOCVD) using both NH3 and DMHy as N-precursors. The relationships between growth rate versus temperature were determined within the range of 300 to 550 °C. The growth of AlN/GaN heterostructures was also investigated herein, employing flow modulation epitaxy MOCVD at 550 °C. Subsequent samples were studied via atomic force microscopy, X-ray diffraction, TEM, and Hall measurements. Two-dimensional electron gases were found in samples where the LT AlN layer was grown with NH3, with one sample showing high electron mobility and sheet charge of 540 cm2/V∙s and 3.76 × 1013 cm−2, respectively. Inserting a LT GaN layer under the LT AlN layer caused the mobility and charge to marginally decrease while still maintaining sufficiently high values. This sets the groundwork towards use of LT nitrides MOCVD in future electronic devices integrating III-nitrides with other materials.

Highlights

Increasing performance and maturity of the III-N material system in electronic applications, such as in high-electron mobility transistors (HEMTs), has made the (Al,Ga)N system an attractive choice for generation electronics [1,2,3]
In this study we report on the further improvement of the properties of the two-dimensional electron gas (2DEG) forming at the interface of AlN layers grown via flow modulation epitaxy (FME) at 550 ◦ C with NH3 and semi-insulating GaN
For low temperature (LT) layers, nitrogen was used as the carry gas, triethylgallium (TEGa) was used as the Ga-precursor, and trimethylaluminum (TMAl) was used as the Al-precursor; NH3 and DMHy were used as N-precursors, with NH3 being used when not otherwise specified

Summary

Introduction

Increasing performance and maturity of the III-N material system in electronic applications, such as in high-electron mobility transistors (HEMTs), has made the (Al,Ga)N system an attractive choice for generation electronics [1,2,3]. It has been shown that pulsed growth schemes can lower impurity incorporation in films [20,21,22,23] Another proposed method towards lowering MOCVD growth temperatures while maintaining film quality has been utilizing alternative precursors which decompose at lower temperatures compared to the standard precursors. In this study we report on the further improvement of the properties of the two-dimensional electron gas (2DEG) forming at the interface of AlN layers grown via FME at 550 ◦ C with NH3 and semi-insulating GaN base layers, which match those of AlN/GaN heterostructures grown under standard conditions. The LT MOCVD grown AlN/GaN heterostructures were analyzed to determine the viability of utilizing these methods on temperature sensitive substrates in the future

Experimental

Results and Discussion

Photograph of LT GaN on GaN

Conclusions