Growth Of GaN Research Articles

Low temperature 2D GaN growth on Si(111) 7 × 7 assisted by hyperthermal nitrogen ions.

As the characteristic dimensions of modern top-down devices are getting smaller, such devices reach their operational limits imposed by quantum mechanics. Thus, two-dimensional (2D) structures appear to be one of the best solutions to meet the ultimate challenges of modern optoelectronic and spintronic applications. The representative of III–V semiconductors, gallium nitride (GaN), is a great candidate for UV and high-power applications at a nanoscale level. We propose a new way of fabrication of 2D GaN on the Si(111) 7 × 7 surface using post-nitridation of Ga droplets by hyperthermal (E = 50 eV) nitrogen ions at low substrate temperatures (T < 220 °C). The deposition of Ga droplets and their post-nitridation are carried out using an effusion cell and a special atom/ion beam source developed by our group, respectively. This low-temperature droplet epitaxy (LTDE) approach provides well-defined ultra-high vacuum growth conditions during the whole fabrication process resulting in unique 2D GaN nanostructures. A sharp interface between the GaN nanostructures and the silicon substrate together with a suitable elemental composition of nanostructures was confirmed by TEM. In addition, SEM, X-ray photoelectron spectroscopy (XPS), AFM and Auger microanalysis were successful in enabling a detailed characterization of the fabricated GaN nanostructures.

Effect of additional N2O gas on the suppression of polycrystal formation and high-rate GaN crystal growth by OVPE method

One of the challenges in the oxide vapor phase epitaxy (OVPE) method is to suppress polycrystal formation for the high-rate growth of thick GaN crystals. In this study, we present the addition of N2O gas as the method to suppress the polycrystal formation in the OVPE-GaN growth. We confirmed that N2O gas could remove the Ga droplet, the origin of polycrystalline GaN. Results showed that the polycrystal density decreased by adding N2O gas. The decline in growth rate with the increase of N2O gas flow rate was smaller compared to that with H2O vapor, which was consistent with the fact that N2O would not affect directly the GaN growth reaction. Furthermore, we obtained a 512-µm-thick OVPE-GaN layer at the growth rate of 128 µm/h, which is the highest value for growing thick GaN layers in the OVPE method.

GaN nucleation on patterned sapphire substrate with different shapes for improved GaN overgrowth

GaN was grown on cone- and dome-patterned sapphire (CPSS and DPSS) at different nucleation times of 40, 80 and 160 s. The GaN was also grown on flat sapphire substrate (FSS) for comparison. The results showed that the GaN growth improved by increasing the nucleation time, except for the case of FSS. Compared to CPSS, DPSS led to better GaN growth. This was due to the geometry of the dome patterns, which had more slanted curvature than cone patterns. Hence, more nucleation was promoted on the trenches and this was desirable to improve the GaN overgrowth. With 160 s of nucleation, the GaN coalescence was better for the growth on DPSS than on CPSS. This resulted in an improved surface of the overgrown GaN layer and lower full-width at half-maximum of XRD (FWHM-XRD) peaks. Strain study showed that the GaN layers grown on DPSS exhibited larger residual in-plane strain than the layers on CPSS due to the achievement of better overgrown GaN. Nonetheless, the strain reduced with nucleation time due to further dislocations inclination. Generally, the GaN layers on FSS showed better crystalline quality than on CPSS and DPSS. However, the layers suffered from larger strain.

Simultaneous Nucleation and Growth of Quaternary Polar and Nonpolar GaN–ZnO Solid Solution Nanowires and Nanorods

Simultaneous Nucleation and Growth of Quaternary Polar and Nonpolar GaN–ZnO Solid Solution Nanowires and Nanorods

Direct growth of GaN on sapphire substrate via polarity transition from N- to Ga-polar using only hydride vapor phase epitaxy

We established a method for directly growing the GaN layer on a sapphire substrate using only hydride vapor phase epitaxy (HVPE). The important factors that affect the manufacture of high-quality, low-cost, and large-diameter GaN substrates require a growth method that does not utilize either a GaN template or processes other than HVPE. N2 carrier gas and a high temperature are important growth parameters required to achieve the direct growth of the GaN layer on the sapphire substrate. The mechanism of the direct growth of the GaN layer on the sapphire substrate reveals that the N-polar GaN layer grows during the initial growth stage via the nitridation of the sapphire substrate and Ga-polar GaN is subsequently produced via polarity inversion. Furthermore, the dislocation density of the GaN layer directly grown on the sapphire substrate is lower than that of the GaN layer grown on a GaN template using metal-organic vapor phase epitaxy.

Interfacial adhesion strength of III-N heterostructures

Wide bandgap semiconductors such as group III-nitrides and SiC are considered as key materials for the fabrication of smaller, more reliable and efficient power electronics. Fabrication of robust and durable power devices requires an optimized design based on the understanding of the interfacial adhesion properties of the constituent thin-film heterostructures. In this study, the adhesion properties of GaN/AlN layers grown on Si substrates were investigated. Particularly, the influence of the AlN buffer layers, necessary for GaN growth on Si, on the delamination response was determined. The interfacial adhesion strength was obtained using cross-sectional nanoindentation (CSN) and four-point bending (4PB) tests. Analytical models based on beam- and elastic plate theory which were applied respectively to calculate the interfacial fracture energy (Gic) for both methods are found to be in good agreement provided the loading conditions are similar. Detailed transmission and scanning electron microscopy investigations prior and subsequent to delamination reveal the microstructural details of the relevant interfaces and provide insights into the encountered mechanisms of interfacial failure. Finally, the probability of delamination along the weakest interface is discussed based on a fracture mechanics model.

Near-infrared electroluminescence of AlGaN capped InGaN quantum dots formed by controlled growth on photoelectrochemical etched quantum dot templates

Near-infrared electroluminescence of InGaN quantum dots (QDs) formed by controlled growth on photoelectrochemical (PEC) etched QD templates is demonstrated. The QD template consists of PEC InGaN QDs with high density and controlled sizes, an AlGaN capping layer to protect the QDs, and a GaN barrier layer to planarize the surface. Scanning transmission electron microscopy (STEM) of Stranski–Krastanov (SK) growth on the QD template shows high-In-content InGaN QDs that align vertically to the PEC QDs due to localized strain. A high-Al-content Al 0.9 Ga 0.1 N capping layer prevents the collapse of the SK QDs due to intermixing or decomposition during higher temperature GaN growth as verified by STEM. Growth of low-temperature (830°C) p-type layers is used to complete the p-n junction and further ensure QD integrity. Finally, electroluminescence shows a significant wavelength shift (800 nm to 500 nm), caused by the SK QDs’ tall height, high In content, and strong polarization-induced electric fields.

A synchrotron X-ray topography study of crystallographic defects in ScAlMgO4 single crystals

ScAlMgO4 is a promising material that can be used to fabricate lattice-matched substrates for the epitaxial growth of GaN and InGaN. To improve its crystal quality, we used synchrotron X-ray topography to study the dislocations in a 50.8-mm-diameter ScAlMgO4 single crystal grown via the Czochralski method. Dislocation character was analyzed in terms of Burgers vectors by comparing dislocation contrasts recorded using six g-vectors that represented the m+c, a+c, and c-type crystal planes. The central area of the substrate, which corresponded to the portion grown vertically under the seed crystal, was characterized by millimeter-sized domains bound by mixed-type dislocation arrays with both in-plane and c-axis Burgers vectors. Basal plane dislocations (BPDs) typically formed an arrow-like shape with three branches. Growth striations with alternating high- and low-dislocation-density areas were observed in the diameter-expanding area and high-dislocation-density areas were covered with tangled BPD networks. The mechanisms of dislocation generation, multiplication, and reaction are discussed based on their line directions and dislocation character.

Van der Waals coherent epitaxy of GaN and InGaN/GaN multi-quantum-well via a graphene inserted layer

GaN-based films grown on sp3-bonded single-crystalline substrates can maintain the coherent growth character. However, exfoliating III-nitride films from these substrates proves difficult because of the strong sp3-type covalent bonds between the substrates and epilayers. The sp2-bonded two-dimensional (2D) materials exhibit hexagonal in-plane lattice arrangements and weakly bonded layers, so the GaN epilayer grown on 2D materials can be transferred onto foreign substrates with ease. In this paper, graphene is used as the inserted layer (IL) on freestanding GaN substrate and the van der Waals coherent epitaxy of GaN-based single-crystalline films on such graphene/GaN templates is investigated. Density functional theory computations are performed to probe the transmission of crystallographic information of wurtzite GaN through the graphene IL. The appropriate layer numbers of graphene IL and GaN growth temperature are optimized to demonstrate the coherent epitaxy character. Both theoretical and experimental results support that the coherent epitaxy of GaN can only be achieved by using a monolayer graphene IL, and the crystalline quality of optimized GaN film can reach the same level of that grown directly on GaN freestanding substrates.

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

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.

Plasma assisted molecular beam epitaxial growth of GaN with low growth rates and their properties

A systematic investigation on PA-MBE grown GaN with low growth rates (less than 0.2 µm/h) has been conducted in a wide growth temperature range, in order to guide future growth of sophisticated fine structures for quantum device applications. Similar to usual growths with higher growth rates, three growth regions have been revealed, namely, Ga droplets, slightly Ga-rich and N-rich 3D growth regions. The slightly Ga-rich region is preferred, in which GaN epilayers demonstrate optimal crystalline quality, which has been demonstrated by streaky RHEED patterns, atomic smooth surface morphology, and very low defect related yellow and blue luminescence bands. The growth temperature is a critical parameter to obtain high quality materials and the optimal growth temperature window (~ 700–760 °C) has been identified. The growth rate shows a strong dependence on growth temperatures in the optimal temperature window, and attention must be paid when growing fine structures at a low growth rate. Mg and Si doped GaN were also studied, and both p- and n-type materials were obtained.

(Invited) Developments of Wbg GaN-on-GaN Vertical Power Devices & Uwbg Ga2O3, Algao, and Heterostructures

In this talk, metalorganic chemical vapor deposition (MOCVD) development of GaN-on-GaN targeting for vertical power devices will be presented. To achieve vertical GaN PN diodes with high breakdown voltage (Vbr) and low on resistance (Ron), it is critical to develop thick GaN drift layer with low controllable doping (Nd-Na) and high electron mobility. Key impurities in MOCVD GaN serving as charge compensation centers were identified. For example, mechanisms of Fe incorporation in MOCVD GaN were identified and addressed [1]. Source of C incorporation is mainly from metalorganic precursor (TMGa), and the C concentration in GaN is highly dependent on MOCVD growth condition, particularly the growth rate. Typically, as GaN growth rate increases, C incorporation increases undesirably. To address this key challenge for achieving high quality thick GaN drift layer, we developed a laser-assisted MOCVD (LA-MOCVD) growth technique to enable fast GaN epitaxy while suppressing C incorporation. The effects of LA-MOCVD GaN growth parameters on GaN growth rate, impurity incorporation and charge transport properties will be discussed. GaN PN diodes with breakdown voltage ~ 3kV are demonstrated.This talk will also discuss our recent developments of ultrawide bandgap (UWBG) Ga2O3, (AlxGa1-x)2O3, and heterostructures [2-5]. Challenges and opportunities for developing (AlxGa1-x)2O3 on Ga2O3 substrates with different crystal orientations ((010), (100), (-201)) be discussed. Band offsets between AlGaO/GaO heterostructures were determined based on high quality epitaxy of AlGaO/GaO heterostructures. Experimental results agree very well with the values predicted from theoretical density functional theory (DFT). Growth techniques based on MOCVD and low pressure chemical vapor deposition (LPCVD) will be compared and discussed. Acknowledgement: The authors acknowledge the funding support from Advanced Research Projects Agency-Energy (ARPA-E) DE-AR0001036, U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office, FY18/FY19 Lab Call, the Air Force Office of Scientific Research FA9550-18-1-0479 (AFOSR, Dr. Ali Sayir) and the National Science Foundation (1810041, 1755479, 2019753). [1] Y. Zhang, Z. Chen, W. Li, H.-S. Lee, M. R. Karim, A. R. Arehart, S. A. Ringel, S. Rajan, H. Zhao, J. Appl. Phys., 127, 215707, 2020.[2] Z. Feng, A F M A. U. Bhuiyan, M. R. Karim, H. Zhao, Appl. Phys. Letts., 114, 250601, 2019.[3] A F M A. U. Bhuiyan, Z. Feng, J. M. Johnson, Z. Chen, H. -L. Huang, J. Hwang, H. Zhao, Appl. Phys. Lett., 115, 120602, 2019.[4] A F M A. U. Bhuiyan, Z. Feng, J. M. Johnson, H.-L. Huang, J. Sarker, M. Zhu, M. R. Karim, B. Mazumder, J. Hwang, and H. Zhao, APL Materials, 8, 031104, 2020.[5] A F M A. U. Bhuiyan, Z. Feng, J. M. Johnson, H.-L. Huang, J. Hwang, and H. Zhao, Appl. Phys. Letts, 117, 252105, 2020.

(Invited) Prospects for MOCVD Growth of GaN for 10kV Power PN Diodes

GaN wide-bandgap semiconductors have superior electronic material properties compared to Si and even SiC that will enable the foundational diodes and transistors for the next revolution in power management technology. To date, GaN pn diodes with 33 μm thick, lightly n-type doped drift layers have been demonstrated with breakdown voltages of 5 kV. [1] However, applications requiring higher blocking voltages could operate with greater efficiency and higher frequency if GaN based diodes and transistors could be proven. Simulations indicate that GaN pn diodes with blocking voltages of 10 kV require drift layers at least 50 μm thick and with carrier concentration less than 3x1015 cm-3. Achieving such demanding such material requirements presents significant challenges for GaN growth processesHydride Vapor Phase Epitaxy (HVPE) is the growth process of choice for very thick GaN layers due to its high growth rate (>50 μm/hr) and is a prevalent method for producing free-standing N+ GaN substrates. This growth technique and its use of carbon free precursors is a natural choice for growth of 50+ μm thick drift layers needed for 10 kV pn diodes. However, Si from the quartz growth chamber used in conventional hot-wall HVPE system leads to difficulty in controllably achieving low carrier concentrations and thus new materials and equipment designs for the growth chamber are being developed. [2] Furthermore, it is challenging to maintain smooth surface morphology of thick HPVE grown GaN epilayers and to grow p-type GaN epilayers that are needed for continuously grown pn diodes. Anode formation by epitaxial regrowth using Metal-Organic Chemical Vapor Deposition (MOCVD) or Mg implantation and annealing have yet to demonstrate multi-kilovolt diodes with reverse leakage currents equal to the best, continuously grown diodes grown by MOCVD.The low growth rate (< ~5 μm/hr) for MOCVD and the use of carbon containing precursors make it a suspect process for producing the > 50 μm thick, lightly doped (< 3x1015 cm-3) drift layers needed for 10 kV diodes. However, large substrate capacity, high up-time MOCVD reactors running highly-efficient, mature manufacturing processes developed for commercial production of visible LEDs could prove attractive for GaN pn diodes when compared to immature, quartz free HVPE reactors that to date have much lower wafer capacity. Further increasing the growth rate of the HPVE process offers diminishing returns in reducing the overall production cycle time, while modest advances in the growth rate of the MOCVD process would significantly reduce in cycle time.Since the lower growth rate of MOCVD might not be disqualifying, the concern shifts to controlling electron concentration at the low levels (< 3x1015 cm-3) in GaN epilayers where the background carbon concentration is at a similar level due to the use of carbon containing precursors. In this presentation we will discuss MOCVD growth and Si doping of GaN epilayers up to 60 μm thick and the properties of pn diodes with 50 μm thick drift layers. We find that carrier concentration is linear with Si flow down to 1x1015 cm-3, the limit of the mercury probe capacitance voltage system, and that the carrier concentration is independent of epilayer thickness from a few microns to 60 microns showing that the MOCVD process is stable for growth of thick drift layers required for 10 kV diodes. We find that controlling the surface morphology is the greatest challenge to producing 10kV-class pn diode devices and discuss how various elements such as surface mis-cut and substrate vendor affect surface morphology. While more work is needed, our studies suggest that MOCVD growth is capable of producing epilayers required for GaN pn power diodes with breakdown voltages of 10 kV.The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy under the PNDIODES and OPEN+ programs directed by Dr. Isik Kizilyalli. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. H. Ohta et al., J. J. Appl. Phys., 57, 04FG09 (2018).H. Fujikura et al., Appl Phys. Lett. 117, 012103 (2020).

Development of GaN HEMTs Fabricated on Silicon, Silicon-on-Insulator, and Engineered Substrates and the Heterogeneous Integration.

GaN HEMT has attracted a lot of attention in recent years owing to its wide applications from the high-frequency power amplifier to the high voltage devices used in power electronic systems. Development of GaN HEMT on Si-based substrate is currently the main focus of the industry to reduce the cost as well as to integrate GaN with Si-based components. However, the direct growth of GaN on Si has the challenge of high defect density that compromises the performance, reliability, and yield. Defects are typically nucleated at the GaN/Si heterointerface due to both lattice and thermal mismatches between GaN and Si. In this article, we will review the current status of GaN on Si in terms of epitaxy and device performances in high frequency and high-power applications. Recently, different substrate structures including silicon-on-insulator (SOI) and engineered poly-AlN (QST®) are introduced to enhance the epitaxy quality by reducing the mismatches. We will discuss the development and potential benefit of these novel substrates. Moreover, SOI may provide a path to enable the integration of GaN with Si CMOS. Finally, the recent development of 3D hetero-integration technology to combine GaN technology and CMOS is also illustrated.

An inductively coupled plasma metal organic chemical vapor deposition based on showerhead structure for low temperature growth

An inductively coupled plasma metal organic chemical vapor deposition (ICP-MOCVD) based on showerhead structure is proposed for the low temperature growth of thin solid films including GaN. The flow field of precursors in the chamber of ICP-MOCVD was analyzed and the structure of showerhead was optimized by changing the showerhead diameter to obtain uniform velocity field above the substrate. The thickness non-uniformity of GaN films grown at 600 °C was improved from 5.14% to 1.86% after the optimization of showerhead. On that basis, the influence of triethylgallium (TEG) and trimethylgallium (TMG) on low-temperature GaN growth were investigated and TEG was proved to be the more appropriate Ga source in this case. Finally, GaN film with high c-axis and in-plane orientations was obtained on sputtered AlN/sapphire template and the full width half maximums of (002) and (102) x-ray rocking curves are 0.45° and 0.57° respectively. Our results provide a practicable method for the optimization of low-temperature MOCVD, which has potential to obtain large-scale crystalline films at low temperature.

Emission characteristics of GaInN/GaN multiple quantum shell nanowire-based LEDs with different p-GaN growth conditions

Abstract Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.

Control of the formation of self-assembled nano-voids at the GaN/GaAs interface

The self-assembling of nanovoids with a precisely controlled depth at the GaN/GaAs interface is reported and their formation mechanism discussed. During the very early stages of GaN growth by molecular beam epitaxy over GaAs(100) misoriented substrates, nano-pits are formed by chemical reactions of gallium and nitrogen with a GaAs sacrificial layer. The GaAs sacrificial layer is grown on top of a GaAs/AlGaAs superlattice that is used to efficiently stop the in-depth etch and to promote lateral etching. Thus, a nanostructure of wide voids and pedestals is self-assembled and confined at the interface. As an application, the lift-off of GaN epilayers from the substrate was carried out successfully, a fact that opens up the applicability of this process in other semiconductor systems.

The Influence of the Preheating Temperature of the (−2 0 1) β-Ga2O3 Substrates on c-Plane GaN Epitaxial Growth

In this paper, we demonstrate the direct epitaxial growth of c-plane GaN on a preheated (−2 0 1) β-Ga2O3 single-crystal substrate with no interlayer or pre-patterning processes by using the atmospheric pressure metalorganic chemical vapor deposition method. The results show that high-temperature preheating (&gt;500 °C) can modify the surface morphology of the substrate so that the crystalline quality of the grown GaN layer can be improved. With higher preheated temperatures, the grown GaN layer reveals smaller FWHM (full width at half-maximum) of the X-ray rocking curve. In addition, we find that the photoluminescence spectra of the GaN layers reveal their narrowest linewidth at a preheated temperature of 800 °C. These results support improvements of crystalline quality and provide optimization of a c-GaN grown epitaxially on the preheated (−2 0 1) β-Ga2O3 substrates for further device fabrication.

Growth and characterization of cubic GaN grown on GaAs (110) substrate by MOVPE

GaN layers were grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on GaAs (110) substrate at temperature varying in the range of 750–900 °C. 50 nm-thick GaN layer grown at low temperature (550 °C) was used as buffer layer. Scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HRXRD) and room temperature cathodoluminescence (RT-CL) studies were carried out and showed a large dependence of the crystalline and optical properties of GaN layer with the growth temperature. A mixture of cubic and hexagonal GaN phases is evidenced by the 2θ/ω spectra which are dominated by a broad peak associated to c-GaN (220) and h-GaN (11.0) reflections. The cubic GaN phase is maximal for a growth temperature of 850 °C. At this temperature, morphological observations by AFM showed the presence of c-GaN islands and RT-CL spectra showed only c-GaN (3.23 eV) emission whereas both emissions of c-GaN (3.23 eV) and h-GaN (3.39 eV) were observed at 900 °C.

Structural and ultraviolet photo-detection properties of laser molecular beam epitaxy grown GaN layers using solid GaN and liquid Ga targets

GaN epitaxial layers have been grown on sapphire (0001) substrate by laser molecular beam epitaxy technique using laser ablation of polycrystalline GaN solid and liquid Ga metal targets in the ambient of nitrogen plasma. In-situ reflection high energy electron diffraction and exsitu atomic force microscopy observations revealed that GaN growth using solid target yields rough surface under three-dimensional growth mode while a flat surface GaN is obtained using liquid Ga target. From X-ray rocking curve measurement, it is also observed that the GaN layer grown using solid GaN target has a relatively better structural quality. X-ray photoelectron spectroscopy confirmed Ga–N bond formation and near-stoichiometric composition of the GaN epilayers. The influence of threading dislocation density on the ultraviolet (UV) photoresponse properties of GaN layers have been studied using metal-semiconductor-metal (MSM) based device structure. It is found that the GaN MSM structure obtained using solid GaN target with lesser screw and dislocation densities exhibits a higher responsivity with fast response and recovery time.