Strain control of AlGaN/GaN high electron mobility transistor structures on silicon (111) by plasma assisted molecular beam epitaxy

Abstract

This paper reports on the use of plasma assisted molecular beam epitaxy of AlGaN/GaN-based high electron mobility transistor structures grown on 4 in. Si (111) substrates. In situ measurements of wafer curvature during growth proved to be a very powerful method to analyze the buffer layer's thickness dependent strain. The Ga/N ratio at the beginning of growth of the GaN buffer layer is the critical parameter to control the compressive strain of the entire grown structure. An engineered amount of compressive strain must be designed into the structure to perfectly compensate for the tensile strain caused by differences in the thermal expansion coefficient between the epi-layer and substrate during sample cool down from growth temperatures. A maximum film thickness of 4.2 lm was achieved without the formation of any cracks and a negligible bow of the wafers below 10 lm. Measurement of the as-grown wafers revealed depth profiles of the charge carrier concentration comparable to values achieved on SiC substrates and mobility values of the two dimensional electron gas in the range 1230 to 1350 cm2/Vs at a charge carrier concentration of 6.5-7 1012/cm2. First results on processed wafers with 2 lm thick buffer layer indicate very promising results with a resistance of the buffer, measured on 200 lm long contacts with 15 lm pitch, in the range of R>109 X at 100V and breakdown voltages up to 550 V

Stress evolution of GaN/AlN heterostructure grown on 6H-SiC substrate by plasma assisted molecular beam epitaxy

“…8 Moreover, the chosen III/V ratio of AlN is also well within the suggested range in order to suppress the silicon carry-over from the SiC substrate to the layers grown subsequently. 7,20,21 As shown in Fig. 8 (a), the stress in AlN is tensile for all the samples except for AlN with III/V ∼ 1 that shows compressive stress.…”

Threading dislocation propagation in AlGaN/GaN based HEMT structures grown on Si (111) by plasma assisted molecular beam epitaxy

“…In this way, the characterization helped to select and adjust the growth parameters for GaN-on-Si state-of-art HEMTs. These structures and its growth processes are wider described in previous works [28]. Some TEM results on TD quantifications in similar materials have been presented [16,21]; however, the study presented in this work is one of the most extensive ones for TDs in wurtzite materials using the combination of planar view-TEM (PVTEM) and cross section-TEM (XTEM) preparations of the observed samples and recent understanding on the TD observation [29].…”

“…For the calculations, M III-N /M Si ¼1.7 and h Si ¼675 mm has been used. Details of the analysis are described elsewhere [28] and are not repeated here…”

“…In S3 an AlN/GaN superlattice (SL) was inserted between AlN nucleation layer and GaN layer. Details of the growth process are given elsewhere [28]. The investigated structures are given in Table 2.…”

Контроль Упругих Напряжений С Помощью Оптической Системы Измерения Кривизны Подложки При Росте Гетероструктур III-N Методом Молекулярно-Пучковой Эпитаксии

“…Коммерчески выпускаемые многолучевые лазерные системы для таких измерений эффективно используются главным образом при газофазной эпитаксии из металлорганических соединений (ГФЭ МОС) ГС на основе III−N [6]. Хотя в литературе сообщается об использовании этого метода и в МПЭ [3,7], но при этом возникает целый ряд проблем. Прежде всего, точность измерений расстояния между отраженными лазерными лучами ограничена низкой частотой измерений (< 1 Hz) и дрожанием ( " wobbling") подложки в процессе роста из-за несовершенства механизма ее вращения во всех известных нам установках МПЭ.…”