GaN Epilayer Grown on Ga2O3 Sacrificial Layer for Chemical Lift-Off Application

Abstract

GaN-on-sapphire structure with a Ga2O3 sacrificial layer was employed for the chemical lift-off process application. The (¯201) β-oriented Ga2O3 thin film was first deposited on the c-plane sapphire substrate using pulsed laser deposition, followed by the GaN growth via metalorganic vapor phase epitaxy under N2 and H2 environment in sequence. From the transmission-electron-microscopy observation, the orientation relationship between GaN and β-Ga2O3 was identified as GaN[11¯20]_Ga2O3[010]. A GaN epilayer with an electroplated copper substrate was demonstrated using a chemical lift-off process where the Ga2O3 sacrificial layer can be laterally etched out with a hydrofluoric solution

Epitaxy of III-Nitrides on β-Ga2O3 and Its Vertical Structure LEDs

“…Despite the high chemical stability of β-Ga 2 O 3 , the growth of III-Nitrides (Al x Ga 1-x N, x from 0 to 1) on β-Ga 2 O 3 substrate should be carried out in a nitrogen atmosphere. As the following chemical equations show, Ga 2 O 3 will decompose under a hydrogen atmosphere at the growth temperature of HT-GaN [106,107]:Ga 2 O 3 + 2H 2 → Ga 2 O + 2H 2 O Ga 2 O + H 2 → 2Ga + H 2 O…”

“…As Figure 7c shows, the absence of Ga 2 O 3 peaks indicate that gallium oxides will fully decompose as time goes on. However, as shown in Figure 7d, the N 2 atmosphere will deteriorate the crystalline quality albeit instrumental for preventing Ga 2 O 3 from decomposition [106]. It can be attributed to the different conversion and diffusion properties of the reactants under N 2 and H 2 atmospheres.…”

“…As mentioned before, the growth of GaN should be performed under a nitrogen atmosphere to protect Ga 2 O 3 . Tsai et al demonstrated a regrowth method to improve the crystalline quality of epilayers that deteriorated by N 2 atmosphere [106]. After the growth of low-temperature (LT) and high-temperature (HT) GaN under N 2 at 530 °C and 915 °C, respectively, GaN was regrown under an H 2 atmosphere at a temperature of 965 °C, as illustrated in Figure 9.…”

“…As mentioned above, the laser lift-off technique is one way to fabricate vertical structure LEDs, but will lead to additional defects and a rough surface to devices resulting from the high energy laser irradiation [40,41,42], while chemical lift-off will not damage the interface between epilayer and substrate [43]. Recently, researches have been carried out for chemical lift-off of GaN using various interlayers [43,44,45,46,47,48,106,107,114,115,116,117,118,119,120]. Lin et al demonstrated the CLO process of InGaN-based LEDs grown on triangle-shaped and truncated-triangle-striped patterned sapphire substrates employing AlN as a sacrificial layer [115,116].…”

Chemical lift‐off process for nitride LEDs from an Eco‐GaN template using an AlN/strip‐patterned‐SiO2 sacrificial layer

“…Since the chemical lift‐off (CLO) method can be employed in the LED device without physical and thermal shocks, this technique has attracted much interest for the substrate removal in recent years . Until now, materials such as CrN , ZnO , Ga 2 O 3 , and patterned‐SiO 2 have been presented as the sacrificial layers and used in the CLO process for the fabrication of the vertical‐type LEDs. Also the removed sapphire substrate from CLO process can be practically reused.…”