Metalorganic chemical vapor phase epitaxy of gallium‐nitride on silicon

Abstract

GaN growth on Si is very attractive for low-cost optoelectronics and high-frequency, high-power electronics. It also opens a route towards an integration with Si electronics. Early attempts to grow GaN on Si suffered from large lattice and thermal mismatch and the strong chemical reactivity of Ga and Si at elevated temperatures. The latter problem can be easily solved using gallium-free seed layers as nitrided AlAs and AlN. The key problem for device structure growth on Si is the thermal mismatch leading to cracks for layer thicknesses above 1 µm. Meanwhile, several concepts for strain engineering exist as patterning, Al(Ga)N/GaN superlattices, and low-temperature (LT) AlN interlayers which enable the growth of device-relevant GaN thicknesses. The high dislocation density in the heteropitaxial films can be reduced by several methods which are based on lateral epitaxial overgrowth using ex-situ masking or patterning and by in-situ methods as masking with monolayer thick SiN. With the latter method in combination with strain engineering by LT-AlN interlayers dislocation densities around 109 cm -2 can be achieved for 2.5 µm thick device structures.

Non‐polar group‐III nitride semiconductor surfaces

“…Cleaving group-III nitride semiconductors grown on Si(111) substrates along (1120) or (1010) planes [70] typically yields surfaces with high step densities [26,71]. On highly stepped (1010) cleavage surfaces of n-type GaN/ Si(111), STS experiments [71] show a pinning of the Fermi energy about 1 eV below the conduction band minimum, in agreement with the above-reported results for free-standing GaN [18].…”

Direct measurement of the band gap and Fermi level position at InN(112¯)

“…3 The samples were cleaved in ultrahigh vacuum along the ͑110͒ plane of the Si substrate and therewith along the ͑1120͒ surface of the deposited wurtzite structure AlN and InN layers. 12,13 For the investigation a homebuilt scanning tunneling microscope with an SPM 1000 ͑RHK͒ control unit was used. Figure 1͑a͒ shows an overview STM image of the crosssectional cleavage surface through the InN/AlN/Si layers.…”

Correlation of Selected Problems During Gan Movpe Epitaxy on si Substrates with in–Situ Interferometer Observation

“…Calculating dislocation densities one can obtain values of the order of 10 × 10 13 cm −3 present at GaN/Si interface. The initial dislocation density quickly decreases within a few hundred nanometers, this feature is presumed to be caused by the high binding and dislocation activation energies of nitrides [1]. Another consequence of large lattice mismatch is the difficulty to grow the layer formed in continuous matter, to completely transit to two-dimensional growth (Fig.…”

“…3). Once initiated, it is not possible to stop this phenomenon, which leads to a rough surface with deep hollows in the substrate [1]. Moreover, nitrogen present in one of the precursors, ammonia, at high temperatures reacts with silicon forming a Si x N x amorphous layer [2].…”

“…This also provides opportunity towards integration with Si electronics. Along with benefits of using silicon as a substrate many issues arise that have already been eliminated or minimized [1]. Problems occurring during GaN growth on Si can hinder to obtain high quality GaN layers with desirable electrical and optical parameters.…”