r-Plane sapphire 위에 HVPE에 의해 성장한 a-plane GaN에피텍셜층의 V/III족 ratio에 따른 특성 변화
Effects of the V/III ratio on a-plane GaN epitaxial layer on r-plane sapphire grown by HVPE
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V/III족 ratio의 변화에 따른 r-plane의 sapphire 위에 HVPE로 성장한 a-plane GaN 에피텍셜층의 특성변화를 연구하였다. V/III족 ratio가 증가함에 따라서, a-plane (11-20) GaN에 대한 Rocking Curve의 FWHM의 값이 감소하며, 성장된GaN의 표면 거칠기도 감소하고, 성장성도는 증가하다가 V/III족 ratio 7까지는 증가하다가 다시 감소하는 경향을 보여준다. 즉 V/III족 ratio 10에서 a-plane (11-20) GaN에 대한 Rocking Curve의 FWHM의 가장 작은 829 arcsec값을 보이고, 표면거칠기도 가장 작은 1.58 nm 값을 보인다. 또한 광학현미경상에서 관찰되는 내부 Crack 또는 void가 가장 적게 발생하였다. 그리고 M모양의 Azimuth angle 의존도를 전 샘플에서 보이며, V/III족 ratio 10에서 FWHM 최대값과 최소값의 편차값이 439arcscec로 가장 작은 차이를 보였다.
Abstract
In this study, effects of the V/III ratio on a-plane GaN epitaxial on r-plane grown by HVPE have beeninvestigated. According to increasing of V/III ratio, the value of FWHM of a-plane (11-20) GaN and the value of surfaceroughness (Ra) were decreased. Growth rate of a-plane GaN epitaxial layer were increased until V/III ratio = 7 as theincreasing of V/III ratio, but it was reduced at V/III ratio = 10. At V/III ratio = 10, the FWHM of a-plane (11-20) GaN RCand the surface roughness (Ra) were 829 arcsec and 1.58 nm, respectively, as the lowest value in this study. Also for V/IIIratio = 10, cracks under surface or voids were observed the lowest values in images of optical microscope. An M-shapedazimuthal dependence over 360oangle range was observed for all samples. At V/III ratio = 10, the difference of FWHM ofa-plane GaN between 0oand 90owas 439 arcsec revealed as the lowest value in the 4 samples.
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