Micro-Raman scattering and microphotoluminescence of GaN thin films grown on sapphire by metal-organic chemical vapor deposition

Feng, Zhe Chuan

doi:10.1117/1.1489051

Cited by 31 publications

(11 citation statements)

References 44 publications

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“…26) From Fig. 2, the values of the top GaN E 2 (high) of the investigated samples were extracted and the amount of residual stress in the GaN films was calculated using 22,27,28) • xx = ¦½/k y , where ¦½ is the difference between the extracted peak position of the GaN E 2 (high) peak and the theoretical peak position of the unstrained GaN (567.6 cm ¹1 ), and k y is the strain coefficient (¹4.3 cm ¹1 GPa ¹1 ). 22,28) It was found from the calculated stress results (not shown here) that the GaN strain/stress changes from tensile to compressive with the increase in the number of SL periods, which proves that the stress state of GaN can be controlled by varying the number of SL periods.…”

Section: Resultsmentioning

confidence: 99%

Effect of AlN/GaN superlattice buffer on the strain state in GaN-on-Si(111) system

Ni¹,

He²,

Yang³

et al. 2014

Jpn. J. Appl. Phys.

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The effect of AlN/GaN superlattice (SL) buffer on the strain state in a GaN-on-Si(111) system was studied in detail by room-temperature micro-Raman scattering measurement. An abnormal satellite peak attached to a GaN E 2 peak was observed, which was verified to stem from the compressively strained GaN in SLs. The results indicate that the strain-sensitive GaN E 2 (high) peak in the GaN-on-Si system with AlN/GaN SLs splits into two peaks because the GaN stress state in the top GaN layer is different from that in SLs. The compressive stress in the GaN layer in SLs was introduced by the AlN layer in each SL period because of the lattice mismatch between GaN and AlN, which ultimately counterbalanced the tensile stress in the top GaN during cooling. Such a counterbalance interaction is strongly dependent on the stiffness coefficient of AlN/GaN SLs, which is proportional to the number of periods of SLs and the relative thickness of AlN in SLs. Such two E 2 peaks from GaN enable us to monitor the strain state in the GaN-on-Si system with AlN/GaN SLs quantitatively.

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Section: Resultsmentioning

confidence: 99%

Effect of AlN/GaN superlattice buffer on the strain state in GaN-on-Si(111) system

Ni¹,

He²,

Yang³

et al. 2014

Jpn. J. Appl. Phys.

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“…14,16,17 Raman scattering is a noncontact and nondestructive technique for studying bonding characteristics and stresses and strains. The vibrational modes in hexagonal and cubic GaN have been studied intensively by Raman spectroscopy, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and it shows that Raman spectroscopy is able to distinguish the two phases in GaN. 6,24,26,35 It has been used to study strains in GaN thin film heterostructures.…”

Section: Introductionmentioning

confidence: 99%

Raman studies of GaN/sapphire thin film heterostructures

Hushur

Manghnani

Narayan

2009

Journal of Applied Physics

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Using Raman spectroscopy, we have studied the optical phonon modes of GaN nucleation layers with the thicknesses of 7 and 45nm, grown on sapphire (0001) substrates by metal organic chemical vapor deposition at low temperatures (500–600°C). These layers consisted of mixed hexagonal and cubic phases. The Raman results from mixed phases were compared with those from pure hexagonal layers which were grown at higher temperatures over 1000°C. The E2H and A1(LO) phonon modes are observed at 548 and 733cm−1 for 45nm thick nucleation layer, while the silent low-frequency B1 mode which is forbidden in good quality hexagonal GaN is observed at 314cm−1. The presence of the strong hexagonal modes for GaN nucleation layers of 45nm thick confirms the crystalline nature of the GaN nucleation layer and dominant hexagonal phase in this mixed cubic-hexagonal nucleation layer. The observed frequencies are shifted with respect to the corresponding A1 and E2 phonon modes in hexagonal GaN. The decrease in mode frequency implies the presence of in-plane tensile strain in these GaN nucleation layers of 45nm thick. The Raman scattering spectra taken from different positions on the sample show similar spectral features, indicating that the GaN nucleation layers of 45nm thick are homogeneous in micron scale.

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“…By using standard Raman spectroscopy, previous studies identified these pathways for five different phonon modes in standard bulk samples of GaN having relatively low free carrier concentrations ͑n Ͻ 10 17 cm −3 ͒. 19,20 In the presence of a high free carrier concentration ͑n Ͼ 5 ϫ 10 17 cm −3 ͒, however, the LO phonons become strongly coupled with the presence of plasmons, forming what is commonly referred to as a longitudinal optical phonon-plasmon ͑LPP͒ coupled mode. 21,22 Tsen et al 6 used this coupled mode, in turn, to deduce the lifetime of the A1͑LO͒ phonon and showed an inverse relationship between the rate of decay and the free carrier concentration.…”

Section: Introductionmentioning

confidence: 99%

Temperature and doping dependence of phonon lifetimes and decay pathways in GaN

Beechem

Graham

2008

Journal of Applied Physics

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The lifetimes of polar optical phonons are known to affect both the electrical and thermal performances of gallium nitride ͑GaN͒ based devices. Hence, understanding the dynamical behavior of these phonons in GaN is integral to the elucidation of carrier drift velocities, hot phonon effects, and temperature localization in these nitride semiconductors. To investigate this dynamic behavior, temperature dependent phonon lifetimes were acquired through utilization of the linewidth of the Raman response for GaN samples having various doping types and concentrations. The temperature dependent lifetimes of the four examined phonon modes were then correlated with the Klemens decay model modified to account for four-phonon processes to deduce the decomposition of the zone center phonons. A graphical method that maps this decomposition in the high symmetry directions of the Brillouin zone is also presented. From the variation in lifetime with free carrier concentration, dominant scattering mechanisms are subsequently found for each of four different phonon modes. It is observed that the phonon-carrier interaction directly determines the lifetimes of the polar optical A1 and E1͑LO͒ modes, while the transverse modes into which these longitudinal phonons decay are independent of this interplay. These results indicate that temperature localization likely arises due to the continual emission and reabsorption between the LO phonon modes and the free carriers rather than the persistence of lattice/carrier interaction throughout the entirety of the energy cascade.

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Micro-Raman scattering and microphotoluminescence of GaN thin films grown on sapphire by metal-organic chemical vapor deposition

Cited by 31 publications

References 44 publications

Effect of AlN/GaN superlattice buffer on the strain state in GaN-on-Si(111) system

Effect of AlN/GaN superlattice buffer on the strain state in GaN-on-Si(111) system

Raman studies of GaN/sapphire thin film heterostructures

Temperature and doping dependence of phonon lifetimes and decay pathways in GaN

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