Optical analysis of biaxial stress distribution in Al0.26Ga0.74N/GaN/Si HEMT's

• AlGaN/GaN/Si HEMTs with x (Al) = 0.26% and SiO2/SiN surface passivation were prepared.
• SiO2/SiN passivation increases tensile residual stress probed in Al0.26Ga0.47N barrier.
• PL shows an agreement with RAMAN measurements.
• Tensile stress in the AlGaN barrier layers increases concentration of the 2DEG.

In this paper, Micro-Raman spectroscopy and Micro-Photoluminescence techniques were utilized to quantify the residual stress in Al0.26Ga0.74N/GaN/Si HEMT's for unpassivated and passivated sample by SiO2/SiN layers. One of the issues that can impact device reliability of the HEMT's based GaN, is the mechanical stress induced in the structure. It has been observed that biaxial stress has a linear relationship with the Raman E2 (high), A1 (LO) mode and the luminescent band gap of GaN. A slight blue shift in the PL peak position indicates a compressive stress induced in the GaN layer close to 0.33 GPa and 0.99 GPa before and after passivation respectively, accompanied by a red shift in PL peak position of the Al0.26Ga0.74N barrier layer affirms the existence of a tensile stress around −1.28 GPa and −2.08 GPa for the unpassivated and passivated sample.

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