The Strain Relaxation Of Heteroepitaxy Nanoislans On Patterned Substrates

On account of the unique properties,low dimensional semiconductor materials represented by the nanoislands attracted wide attention by researchers all over the world.The nanoislandss had already been used in QD-LED,Nanoislands Laser,Nanoislands Infrared Photodetector and Nanoislands Semiconductor Optical Amplifier.The driving force of heteroepitaxy nanoislands is the strain caused by the misfit of different semiconductor materials,and the growth of nanoislands follow the S-K growth pattern as a process of strain relaxation,namely,the certain thickness WL appears at first and then the islands begin to grow on it.Actually,the ordering growth of heteroepitaxy nanoislands is the precondition of its use in optoelectronic devices.The technology of heteroepitaxy nanoislands on patterned substrates is a useful way to realize the ordering growth of heteroepitaxy nanoislands.Therefore,from the viewpoint of the growth of heteroepitaxy nanoislands and its use in optoelectronic devices,it is necessary to study the strain relaxation of heteroepitaxy nanoislands on patterned substrates.In this paper,we briefly introduced the pattern of heteroepitaxy nanoislands growth,and we obtained the GeSi nanoislands on Si(001)substrates by pulsed laser deposition.We also introduced the common technology to obtain ordering growth of heteroepitaxy nanoislands.By modeling the GeSi nanoislands on Si(001)substrates,we used FEM to study the influential factors of strain relaxation depending on the continuum elasticity theory.We found that the strain relaxation of dome,barn and cupola shapes of GeSi nanoislands(the AR was 0.2,0.3 and 0.4,respectively)was the exponential function of AR.At last,by using finite element models of pyramid,dome,barn,and cupola GeSi nanoislands inside pit-patterned Si(001)substrates with anisotropic elasticity constants,the influences of aspect ratio,pit inclination angle,and pit filling-level to the elastic relaxation of GeSi nanoislands inside pit-patterned substrates are quantitatively analyzed.The results represent that the relative elastic relaxation of nanoislands inside pits decreases with aspect ratio(pyramid to cupola)at certain inclination angles and pit filling levels.At certain pit inclination angle,the relationships between the normalized elastic relaxation of dome,barn,cupola nanoislands and pit filling level can be described as an exponential function.The description of elastic energy density as an analytical function of nanoislands aspect ratio,pit inclination angle,and pit-filling level is obtained.For a particular aspect ratio of dome and barn nanoislands,both the pit inclination angles obtaining the best elastic relaxation and the pit inclination angles obtaining the same elastic energy density with the nanoislands on flat substrates increase with the pit filling levels.Finally,the conditions for dome and barn nanoislands to position at edge or inside the pit are found.