Growth stresses and cracking in GaN films on (111) Si grown by metal-organic chemical-vapor deposition. I. AlN buffer layers

Srinivasan Raghavan, Joan Marie Redwing

Research output: Contribution to journalArticle

135 Citations (Scopus)

Abstract

Intrinsic stress evolution during the growth of GaN by metal-organic chemical-vapor deposition on (111) Si, using an AlN buffer layer, was monitored in situ with a multiple-beam optical stress sensor. Data show that stress evolution takes place in two stages: an initial compressive regime up to about 100 nm in thickness followed by a transition to a constant tensile stress, ∼0.3 GPa, in films up to 1 μm thick. Correlation of the stress evolution with surface morphological evolution by sequential atomic force microscopy images clearly shows that the incremental stress remains compressive in spite of grain coalescence, which is generally considered to be the dominant source of tensile stress in GaN films on sapphire. Rather, the most dominant feature accompanying the transition in stress from compressive to tensile, which takes place after grain coalescence, is an increase in the lateral size of individual islands. It is shown that this incremental tensile stress accompanied by an increase in lateral grain size can be accounted for by the annihilation of free volume associated with the grain boundaries. On samples cooled to room temperature, surface cracks mainly on the (1010) planes are observed to have channeled in films thicker than 250 nm. Analysis of cracking using the theory of brittle fracture, using the measured growth stress profile and value for the critical thickness, yields a thermal-expansion mismatch stress off 1.1 GPa for GaN films deposited at 1100 °C and cooled to room temperature.

Original languageEnglish (US)
Article number023514
JournalJournal of Applied Physics
Volume98
Issue number2
DOIs
StatePublished - Jul 15 2005

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metalorganic chemical vapor deposition
buffers
tensile stress
coalescing
surface cracks
room temperature
thick films
thermal expansion
sapphire
grain boundaries
grain size
atomic force microscopy
sensors
profiles

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

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abstract = "Intrinsic stress evolution during the growth of GaN by metal-organic chemical-vapor deposition on (111) Si, using an AlN buffer layer, was monitored in situ with a multiple-beam optical stress sensor. Data show that stress evolution takes place in two stages: an initial compressive regime up to about 100 nm in thickness followed by a transition to a constant tensile stress, ∼0.3 GPa, in films up to 1 μm thick. Correlation of the stress evolution with surface morphological evolution by sequential atomic force microscopy images clearly shows that the incremental stress remains compressive in spite of grain coalescence, which is generally considered to be the dominant source of tensile stress in GaN films on sapphire. Rather, the most dominant feature accompanying the transition in stress from compressive to tensile, which takes place after grain coalescence, is an increase in the lateral size of individual islands. It is shown that this incremental tensile stress accompanied by an increase in lateral grain size can be accounted for by the annihilation of free volume associated with the grain boundaries. On samples cooled to room temperature, surface cracks mainly on the (1010) planes are observed to have channeled in films thicker than 250 nm. Analysis of cracking using the theory of brittle fracture, using the measured growth stress profile and value for the critical thickness, yields a thermal-expansion mismatch stress off 1.1 GPa for GaN films deposited at 1100 °C and cooled to room temperature.",
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Growth stresses and cracking in GaN films on (111) Si grown by metal-organic chemical-vapor deposition. I. AlN buffer layers. / Raghavan, Srinivasan; Redwing, Joan Marie.

In: Journal of Applied Physics, Vol. 98, No. 2, 023514, 15.07.2005.

Research output: Contribution to journalArticle

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