Al doping in (1−101)GaN films grown on patterned (001)Si substrate

Abstract

The effect of Al doping on crystalline and optical properties of semipolar (1−101)GaN was investigated. The samples were grown on a patterned (001)Si substrate by selective metal-organic vapor phase epitaxy. The x-ray analyses showed that the strain in the (1−101)GaN layer is reduced substantially by the Al doping. Moreover, the cathode-luminescence (CL) intensity of the band edge emission band was enhanced and the linewidth became narrow. The CL images showed the reduction of dislocation density. These results show that the small amount of Al atoms in GaN improves the crystalline and optical properties. The results are attributed to the dislocation pinning and solution hardening effect due to Al atoms.

Semi-polar GaN LEDs on Si substrate

“…In case of a (0001)GaN grown on (111)Si substrate, during the cooling procedure in the MOVPE chamber, the thermal expansion coefficient difference of 2×10 −6 /K induces strain ε=Δl/l of the order of 2×10 −3 in the grown layer. This has been confirmed by X-ray analyses of a (1-101)GaN grown on (001)Si [13]. We found that the strain along the stripe direction is ε 〈11−20〉 =2.3×10 −3 , which is in agreement with that found in a uniform (0001)GaN on (111)Si.…”

“…By adopting anisotropy etching behavior of Si in a KOH solution, (111) facet is developed easily on a Si substrate with an arbitrary orientation. Thus, Honda et al succeeded in growing (1-101)GaN on (001)Si substrate [8], (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22))GaN on (113)Si substrate [9]. These faces are typical stable semi-polar face of the GaN.…”

Growth of semi‐polar (11‐22)GaN on a (113)Si substrate by selective MOVPE

“…By comparing the values with those reported for unstrained materials, we found the magnitude of the strain along the m-axis (or along the stripe direction) was as large as +0.20%, while those along a-and c-axis (perpendicular to the stripe direction) were at -0.05% and +0.02%, respectively. This shows that the sample was subject to not a biaxial stress, but a uniaxial one, which is similar to the case of (1-101)GaN on (001)Si [5].…”

“…To do this, a (111)Si facet was formed on a off oriented (001)Si substrate by anisotropy etching in a KOH solution, and the GaN was grown on the (111) surface selectively. By tilting the crystal axis of the GaN on the substrate surface, we have achieved a GaN layer with low dislocation density and reduced strain [5]. The (111) plane of the Si forms an angle of 54.7 degree against the (001) plane.…”

Maskless selective growth of semi-polar (112¯2) GaN on Si (311) substrate by metal organic vapor phase epitaxy

“…The large difference, however, in lattice constant (17%) and thermal expansion coefficient (56%) is still remained as an obstacle for obtaining good quality of III-nitrides [1]. There have been many reports on the attempts to reduce strain/stress by using patterned silicon substrates for the growth of semi-polar GaN [2][3][4][5][6][7]. For the growth of semi-polar (11 0 1) GaN or (11 2 2) GaN, (0 0 1) Si substrates or (3 11) Si substrates are usually used, on which etched patterns are formed for the exposure of (111) Si facets.…”