Review of final qualification work "Core structure of dislocations and recombination properties of gallium nitride" master student of Solid State Electronics Shapenkov Sevastyan Vladimirovich for the master's degree in physics.  The reviewed master thesis is devoted to the study of recombination properties and core structural features of freshly introduced dislocations in gallium nitride crystals. The relevance of the studies is undoubted due to the widespread use of gallium nitride in power, high-frequency and light emitting devices of the visible and ultraviolet lights. Moreover the recently results of as studies show that screw dislocations introduced after the growth of the GaN crystal are an effective source of ultraviolet radiation. The volume of thesis is 51 pages, including 34 figures and a list of used literature from 57 titles. Structurally, the work consists of three chapters: 1) a literary review of gallium nitride with possible configurations of dislocations, 2) descriptions of methods in which the transmission electron microscopy (TEM) method is described in detail, and cathodoluminescence, 3) the results of the work and their discussions. The work was done accurately, with a small number of typos and jargon, separately it should be noted the author's thoughtful use of terms. An exhaustive amount of information on the transmission electron microscopy technique presented in the paper shows the author's desire to fully understand the contrasts obtained by the difficult-to-interpret TEM During the reading of the work, the following questions and comments arose. Remarks: 1) According to the title of the thesis “Core structure of dislocations and recombination properties of gallium nitride” an erroneous idea is created that all dislocations have one common core. 2) In Figure 5, the author deceives the reader by reporting that the reference plane (0001) is the slip plane of dislocations with the Burgers vector along <0001>, which is known to be the direction perpendicular to the (0001) plane. Similar errors are also given for prismatic planes. 3) In the dislocation reaction given on page 10, the directions of the Burgers vectors are indicated using parentheses instead of square brackets. 4) Sometimes font size of the main text changes, which complicates the reading process. Question: 1) What is the difference between the conditions for obtaining TEM images in Figures 31 (A) and 31 (B), based on a comparison of which, the author receives significant data on the specific structure of the butterfly node being formed? Despite all the above remarks, I believe that the work, undoubtedly, deserves an "excellent" evaluation, and its author is awarded a master's degree in physics.  01.06.18  Reviewer  PhD, senior scientist The Ioffe Institute RAS Gorbunov R. I.