The layers of gallium nitride are usually synthesized on heterogeneous substrates. As a result the layers become tense, containing dislocations and VN defects, which are producing deep levels of ntype conductivity and electron concentration of the order of 1020 cm-3. To reduce the concentration of defects, modified the composition of Ga-N to stoichiometry and the radiant recombination to the fundamental transitions region, GaN layers require additional thermal treatment at high temperature in different environments. Treatment improves the surface morphology and increases the photoluminescence intensity, influencing the concentration and mobility of charge carriers. In this paper the research results are presented for the influence of thermal treatment at 800-950°C in nitrogen or vacuum on the photoluminescence spectral distribution and the resistivity of 10 m GaN layers deposited on silicon by HVPE method. The growth of GaN layers on silicon substrates with intermediate layers of AlN was performed by the method of chemical transport reactions in the system (H2-NH3-HCl-Ga-Al), (HVPE) in a reactor of quartz. The pressure in the reactor was higher than atmospheric by 50 mm H2O. As a carrier gas was used hydrogen, purified with a palladium filter. As precursors ammonia, hydrogen chloride, Ga (99.999%), and Al (99.999%) were used. HCl flows in ducts of aluminum, gallium and in the etching one were dissolved in hydrogen flow. The total hydrogen consumption amounted to 4.8 slpm, and the ammonia consumption varied in the range of 0.5 ÷ 2.4 slpm. The HCl consumption varied between 1 ÷ 100 smlpm, depending on the procedures performed. During the deposition, silicon substrates were rotated by a flow of hydrogen, at a speed of100 rot/min, in order to obtain homogeneous coatings. The thermal profile of the reactor was provided by resistive heating with multiple zones, where the temperature is kept constant. The temperature of Al and Ga sources was 850°C, and that of the substrate was 950°C. As substrates, there were used covered Si wafers of КДБ 0,1 trademark having the (111) crystallographic orientation. The thermal treatment of GaN layers was carried out in a flow of nitrogen or in vacuum at a pressure of 10-4 Tor at a temperature of 800°C, 850°C, and 900°C.The spectral distribution of photoluminescence (FL) of GaN layers was investigated at 300 K by using the monochromator MDR-23 with a resolution of 2.6 nm/mm. Excitation of FL was carried out with a nitrogen laser (= = 337 nm), the impulse having a power of7 W/cm2and duration of 10 ns. The radiation signal was recorded with the ФЭУ-51 multiplier in a synchronous detection system.   The FL spectra of untreated GaN layers at 300 K consist of two bands with maxima at 370 and 555 nm. The layers treated in nitrogen or vacuum have the same shape as the untreated ones, and only the relative intensity of peaks changes. In case of layers treated for in nitrogen during one hour, the intensity of the band having the maximum at 370 nm increases with treatment temperature (3 times at 800°C, 5 times at 850°C, and 7 times at 900°C), and the intensity of bands with the maximum at 555 nm decreases insignificantly. At thermal treatment in vacuum, the intensity of both bands is reduced with increasing the treatment temperature. When treating for one hour at 800°C, the intensity of the band with a peak at 370 nm is reduced twice, and the intensity of the one with a maximum at 555 nm - 2.7 times. When increasing the treatment temperature up to 900°C, the intensity of peaks slightly decreases. The conductivity of layers treated in nitrogen was studied. For the untreated layers  is  34 -1cm-1. At the treatment temperature increasing from 800 to 900°C,  is reduced from 16 up to  4 -1cm-1. In GaN layers treated in vacuum at 900°C increases from 1.4 to 42 -1cm-1with increasing the duration of  treatment from one to four hours.