X-ray diffraction study of deformation state in InGaN/GaN multilayered structures

High resolution X-ray diffractometry (HRXRD) was used to investigate InxGa₁₋xN/GaN multilayered structures grown by the metal-organic chemical vapor deposition (MOCVD) method. Deformation conditions in the superlattice (SL) and its separate layers, degree of relaxation in the structure layers, as well as the period of the SL, thicknesses of its layers and composition of InxGa₁₋x solid solution in active area were determined. It was found that SL was grown on the relaxed buffer layer. SL layers were grown practically coherent with slight relaxation of InGaN layer (about 1.5 %). The role of dislocations in relaxation processes was established. Analysis of experimental diffraction spectra in these multilayered structures within the frameworks of ParratSperiozu was adapted for hexagonal syngony structures

Structural and electrical-physical properties of the ohmic contacts based on palladium to n⁺ -n-n⁺⁺ -n⁺⁺⁺ -InP

Presented in this paper are experimental data on structural properties of contact metallization and temperature dependence of the specific contact resistance for ohmic contacts Au–Ti–Pd–n⁺-InP and Au–Ti–Ge–Pd-n⁺-InP prepared using the method of successive thermal evaporation of metals in oil-free vacuum in one process cycle onto the n⁺-n-n⁺⁺-n⁺⁺⁺-InP epitaxial structure heated to 300 °C. It has been theoretically and experimentally shown that within the temperature range 250…380 K the current transport mechanism in the ohmic contacts Au–Ti–Pd–n⁺-InP is thermal-field one, and in the ohmic contacts Au–Ti–Ge–Pd-n⁺-InP it is caused by conductivity along metal shunts linked with dislocations. According to the X-ray diffraction data, the density of these dislocations in the near-contact InP area is ~10⁹ cm⁻²

Ohmic contacts based on Pd to indium phosphide Gunn diodes

Experimental data on manufacturing the ohmic contacts Au–Ti–Pd–n⁺-InP, formed using vacuum deposition of metal onto a heated to 300 °C substrate representing an epitaxial n⁺-n-n⁺⁺-n⁺⁺⁺-InP structure. The specific contact resistance measured at room temperature was about 7·10⁻⁵ Ohm·cm². Voltage-current characteristics within the temperature range 110 to 380 K are linear. Gunn diodes with such contacts, which were made as a straight mesa-structure in a pulsed mode (pulse duration of 100 ns, pulse ratio of 1000, operating current of 2.2 A), generated the microwave power ~10 mW in the V-band

Determination of fundamental optical constant of Zn2SnO4 films

Examined in this paper have been optical properties of polycrystalline films Zn2SnO4 deposited using the spray pyrolysis method within the range of substrate temperatures 250 °C to 450 °C in increments of 50 °C. The spectral dependences have been found for the following physical quantities: k(λ), n(λ), ε1(λ), ε2(λ) and defined as they change under the influence of substrate temperature Тs. Moreover, using the model by Wemple–DiDomenico it was calculated the dispersion energy Ео and Ed for this oxide. Two independent methods defined band gaps Zn2SnO4, which decreases from 4.21…4.22 eV down to 4.04…4.05 eV with increasing Тs from 250 °C up to 450 °C

Determination of fundamental optical constants of Zn2SnO4 films

Examined in this paper have been optical properties of polycrystalline films Zn2SnO4 deposited using the spray pyrolysis method within the range of substrate temperatures 250 °C to 450 °C in increments of 50 °C. The spectral dependences have been found for the following physical quantities: k(), n(), ε1(), ε2() and defined as they change under the influence of substrate temperature Тs. Moreover, using the model by Wemple–DiDomenico it was calculated the dispersion energy Ео and Ed for this oxide. Two independent methods defined band gaps Zn2SnO4, which decreases from 4.21…4.22 eV down to 4.04…4.05 eV with increasing Тs from 250 °C up to 450 °C

Mechanism of strain relaxation by twisted nanocolumns revealed in AlGaN/GaN heterostructures

The structural properties of AlGaN/GaN heterostructures grown by metal organic chemical vapor deposition on sapphire substrates with different thicknesses were studied by high-resolution x-ray diffraction. The relation between the deformations and dislocation densities in the layer and substrate was established. The dependence of the system's curvature on the lattice mismatch, caused by different fractions of nanoblock twists with respect to the c-plane, was determined. A mechanism of elastic strain relaxation was proposed

Синтез, люминесцентные и структурные свойства нанокристаллов Cd1-xCuxS и Cd1 - xZnxS

This paper describes the in-situ synthesis in polymer films of the nanocrystals (NCs) of the ternary semiconductors Cd1 – xCuxS and Cd1 – xZnxS as well as the results of investigations of their structure and optical properties. It has been established that, in case of Cd1 – xCuxS in a large range of Cu to Cd ratios, the hexagonal structure is dominating in NCs synthesized, while in case of Cd1 – xZnxS the dominating crystalline structure of NCs corresponds to cubic structure of CdS. However in both cases formation of separate phases of either CdS and CuS or CdS and ZnS has not been revealed, confirming formation of ternary semiconductor compounds. It has been revealed an opposite effect of increasing concentrations of Cu and Zn cations in ternary compounds on intensity of an impurity photoluminescence, for the former this intensity decreases, but for latter it increases. The possible reasons for these phenomena are discussed.У роботі описується синтез in-situ в полімерних плівках нанокристалів (НК) потрійних напівпро- відників Cd1 – xCuxS і Cd1 - xZnxS, а також результати досліджень їх структури і оптичних властивостей. Встановлено, що у разі Cd1 – xCuxS у широкому діапазоні співвідношень Cu-Cd у синтезованих НК до- мінує гексагональна структура, тоді як у разі Cd1 - xZnxS домінуюча кристалічна структура НК відпові- дає кубічній структурі CdS. Разом з тим, в обох випадках утворення окремих фаз CdS і CuS або CdS і ZnS не було знайдено, що підтверджує утворення потрійних напівпровідникових сполук. Було вияв- лено протилежний вплив збільшення концентрації катіонів Cu і Zn в потрійних сполуках на інтенси- вність домішкової фотолюмінесценції, якщо для перших ця інтенсивність зменшується, то для остан- ніх вона зростає. Обговорюються можливі причини цих явищ.В работе описывается синтез in-situ в полимерных пленках нанокристаллов (НК) тройных полу- проводников Cd1 – xCuxS и Cd1 - xZnxS, а также результаты исследований их структуры и оптических свойств. Установлено, что в случае Cd1-xCuxS в большом диапазоне отношений Cu-Cd в синтезирован- ных НК доминирует гексагональная структура, тогда как в случае Cd1 - xZnxS доминирующая кри- сталлическая структура НК соответствует кубической структуре CdS. Тем не менее, в обоих случаях образование отдельных фаз CdS и CuS или CdS и ZnS не было найдено, что подтверждает образова- ние тройных полупроводниковых соединений. Было выявлено противоположное влияние увеличения концентрации катионов Cu и Zn в тройных соединениях на интенсивность примесной фотолюминес- ценции, если для первых эта интенсивность уменьшается, то для последних она возрастает. Обсуж- даются возможные причины этих явлений