Compensation in (2¯01) homoepitaxial β-Ga2O3 thin films grown by metalorganic vapor-phase epitaxy

Abstract

Homoepitaxial growth of β-Ga2O3 using metalorganic vapor-phase epitaxy (MOVPE) on several different crystal orientations has previously been studied, but growth on the (2¯01) plane has remained comparatively unexplored. To investigate this, we grew Si-doped and unintentionally doped (UID) homoepitaxial layers simultaneously on Sn-doped (2¯01) and (010) substrates under conditions optimized for (010) growth. We report herein on results from current–voltage and capacitance–voltage (IV and CV) and deep level transient spectroscopy (DLTS) characterization of Schottky diodes fabricated on these samples. Devices on (010) display nearly ideal Schottky diode JV and CV behaviors while for (2¯01) evidence of complete depletion of >2 μm thickness, UID epilayers are observed. The (2¯01) UID diodes exhibited Mott–Gurney space charge-limited transport and were completely depleted even at zero bias. Doping (2¯01) samples heavily with Si was sufficient to overcome background compensation and reproduce near-ideal diode behavior. DLTS data from these doped devices show, in addition to typical negative majority-carrier transients, positive transients with a broad energy distribution, possibly indicating traps on structural defects or surface states. An etch pit analysis under SEM revealed intricate structures of the grown layers. Cross-sectional TEM characterization of a (2¯01) sample revealed a high density of structural defects within the epitaxial layer, likely stacking faults. Hypotheses for the origins of the compensation in (2¯01) β-Ga2O3 homoepitaxial MOVPE growth under (010) growth conditions are discussed; the most likely explanation is the presence of defect states introduced by the stacking faults visible under TEM.

Effect of extended defects on photoluminescence of gallium oxide and aluminum gallium oxide epitaxial films

“…studied a similarly MOVPE grown sample like the β-Ga 2 O 3 film grown on (-201) Fe-doped β-Ga 2 O 3 . Using TEM, they showed that the film quality was poor and exhibited multiple extended defects throughout the sample 45 . Additionally, the Si-doped series has comparable growth conditions to the (-201) β-Ga 2 O 3 film grown on a differently oriented β-Ga 2 O 3 substrate, suggesting that growth conditions that could change the number of a specific type of point defect in the sample could be ruled out.…”

Thermal Conductivity of β-Phase Ga2O3 and (AlxGa1–x)2O3 Heteroepitaxial Thin Films

“…However, direct growth on other orientations ((100), (2̅01), and (001)) has led to films with lower mobility due to the higher density of structural defects. , It has been shown that high-quality (100)-oriented β-Ga 2 O 3 thin films can be grown by choosing a β-Ga 2 O 3 substrate with the correct offcut orientation, which suppresses the formation of structural defects . Similar defects have been observed in MOVPE-grown (2̅01) homoepitaxial β-Ga 2 O 3 films . Therefore, both low- and high-quality (2̅01)-oriented heteroepitaxial β-Ga 2 O 3 films were grown in this work using 0° and 6° offcut-angled c -plane sapphire substrates, respectively.…”

“…57 However, direct growth on other orientations ((100), (2̅ 01), and (001)) has led to films with lower mobility due to the higher density of structural defects. 58,59 It has been shown that high-quality (100)-oriented β-Ga 2 O 3 thin films can be grown by choosing a β-Ga 2 O 3 substrate with the correct offcut orientation, which suppresses the formation of structural defects. 60 Similar defects have been observed in MOVPE-grown (2̅ 01) homoepitaxial β-Ga 2 O 3 films.…”

“…60 Similar defects have been observed in MOVPE-grown (2̅ 01) homoepitaxial β-Ga 2 O 3 films. 58 Therefore, both low-and high-quality (2̅ 01)-oriented heteroepitaxial β-Ga 2 O 3 films were grown in this work using 0°and 6°offcut-angled c-plane sapphire substrates, respectively.…”

Phase Stabilized MOCVD Growth of β‐Ga2O3 Using SiOx on c‐Plane Sapphire and AlN/Sapphire Template

“…[4] High-quality homoepitaxial β-Ga 2 O 3 layers and high-performance devices on (010), (001), (100), (201) β-Ga 2 O 3 substrates were demonstrated. [1,11,[14][15][16] However, β-Ga 2 O 3 substrates have low thermal conductivity (%0.27 W cm À1 K), which is not suitable for power semiconductor devices. [17] Developing β-Ga 2 O 3 heteroepitaxy on thermally conductive materials like AlN/sapphire template, bulk AlN or 4H-SiC or 6H-SiC substrates can improve heat dissipation in power devices.…”