Specialists at the A.F. Ioffe Institute of Applied-Physics (Russian Academy of Sciences) have developed a new methodology for nano-dimensional heterostructure composition analysis. Along with the composition, the depth of layer occurrence is also identified. Experimental check of the methodology has proved that the data obtained through it on semiconductor structure constitution well agrees with measurement results achieved by other method, the data having low error.

Layer structures consisting of semiconductors with different width of forbidden band (i.e., with different conductivity) are known as heterostructures. Development of such materials is one of the most promising directions in nanotechnology advance. The 2000 Nobel prize was awarded to Academician Zh. I. Alferov for “advancement of semiconductor heterostructures for high-speed optoelectronics”.

At the moment, heterostructures have found wide application in optoelectronics, various light-emitting diodes (LEDs). Their utilization in solar batteries also seems very promising. Researchers’ special attention is drawn by heterostructures with nano-dimensional semiconductor layers. However, at the moment there exists no universally recognized method for analysis of such materials, which creates great problems for their practical application.

Tatiana Popova and her colleagues at the A.F. Ioffe Institute of Applied Physics, Russian Academy of Sciences, have developed a new method for analysis of heterostructure composition with nano-dimensional layers and have written the software that enables to identify composition and the depth of analyzable structure and the depth of its layer occurrence. The work was published in the “Semiconductor Physocs and Technology”  journal.

X-ray spectroscopic analysis is one of widely applicable methods for analyzing substance. The substance is exposed to X-ray impact, atoms get actuated, thus enabling to judge about the specimen qualitative and quantitative composition by the amount of secondary X-rays quanta radiated by them. However, this method has an inadmissibly low accuracy when investigating nano-dimesional heterostructures because the layer depth is too small.

The researchers have developed a new algorithm of X-ray spectroscopic microanalysis that allows to reduce error of method. The signal is processed by a special program, which introduces a correction for small layer dimension. The layer dimension data required to this end is preliminary obtained via transmission electron microscopy. Besides, the obtained signal is compared to calibration signals obtained from substances of known composition, which also improves material identification accuracy.

To check the method, some samples of InGaAs and ZnCdSe (indium-gallium-arsenic and zinc-cadmium-selenium) heterostructures were measured. The researchers have confirmed that the material composition/structure data obtained via the new method well agrees with the data obtained via analyzing by X-ray diffraction and transmission electron microscopy, and it has low error. The researchers point out that the obtained results can be used to control the new heterostructure creation technology.

Source of information: “X-ray spectroscopic microanalysis of heterostructures with nano-dimensional layers”. Semiconductor Physics and Technology, 2011, Vol. 45, issue 2

Further information: Tatiana Borisovna Popova, A.F. Ioffe Institute of Applied-Physics, Russian Academy of Sciences, Tel.: + 7(812)292-73-93 E-mail: T.Popova@mail.ioffe.ru

Zamorianskaya Maria Vladimirovna, A.F. Ioffe Institute of Applied-Physics, Russian Academy of Sciences, Tel.: + 7 (812)292-73-93 E-mail: Zam@mail.ioffe.ru