Mechanism of light emission and manufacturing process of vertical-type light-emitting diode grown by hydride vapor phase epitaxy

Abstract

We developed a vertical-type light-emitting diode (LED) in which the substrate is removed using a hydride vapor phase epitaxy (HVPE) apparatus consisting of a multi-graphite boat filled with a mixed source and a high-temperature (T ≈ 900 °C) RF heating coil outside the source zone. The new chip-growth process with a significant reduction in the number of production steps is completed in only four steps, namely, photolithography, epitaxial layer growth, sorting, and metallization. We analyze the emission mechanism of these lights from measurement results to validate the characteristics of the light emitted from these vertical-type blue LEDs and white LEDs (WLEDs) without substrates, and propose that this mixed-source HVPE method may be a promising production technique for LEDs.

Optical property of hexagonal (2H) silicon crystal

“…The first step (see figure 1(b)) for the growth of a 2H Si crystal (or needle) on Si(111), involving nitridation by NH 3 gas, is a melt-back step by GaCl n and AlCl gases among the various gaseous phases generated by the flow of a HCl source gas over the mixed source. NH 3 in the growth of 2H structured Si seems to play a nitridation role, preventing the oxidation of the Si(111) substrate, and acts to activate a Si-Al compound (amorphization state) to be seated on the Si(111) substrate [22][23][24]. The second step (see figure 1(c)) is a nucleation step that commences with the synthesis between the NH 3 gas and the gaseous phases (AlCl and GaCl n ) [22][23][24][25][26][27][28].…”

“…In the present work, we employed hydride vapor phase epitaxy (HVPE) to 2H structured Si crystals at approximately 1200 • C over a period of 2 h. The mixed-source HVPE approach, combining both in situ HVPE technology and liquid phase epitaxy methods with a mixed source, differs from the continual supply of source materials as used in metal organic chemical vapor deposition (CVD) and other existing HVPE methods [22,23].…”

Fabrication of selective-area growth InGaN LED by mixed-source hydride vapor-phase epitaxy

“…Source gases such as HCl, N 2 , and NH 3 were jetted through two quartz tubes for the growth of the epilayers. [23][24][25][26][27][28][29][30][31] Table I shows the growth conditions and measured results of epilayers consisting of a bare chip with an In composition of 11.0% in the active layer. By using a multi-graphite boat filled with the mixed source of In and Ga, the SAG epilayers were deposited by the mixed-source HVPE method on an n-type GaN substrate to fabricate the SAG InGaN LEDs.…”

“…[17][18][19][20][21][22] Over the years, we have developed a simplified process for manufacturing a vertically structured LED without a substrate by a mixed-source HVPE method. 23) The mixed-source HVPE equipment consists of a source zone with an RF heating coil, which is used to control high temperatures (T > 900 °C) and to easily regulate the change in temperature; a multi-graphite boat filled with the mixed source, to insulate against high temperatures and for the control of growth rate through the adjustment of the quantity of the mixed source; and a growth zone with three furnaces. The setup is different from that of previously reported HVPE methods.…”

“…[23][24][25][26][27][28][29][30][31] The fabrication of the LED by the mixedsource HVPE method is based on the consecutive growth of all epitaxial layers using a multi-graphite boat filled sequentially with mixed-source materials in the source zone at high temperatures (T > 900 °C). 23) This mixed-source HVPE method has the advantages of low manufacturing cost owing to the reduced number of manufacturing steps, consecutive growth of epilayers using the multi-graphite boat, and ease of doping by regulating the mixing ratio of source materials. As a result, we have successfully grown a high-quality AlN epilayer directly on a patterned sapphire substrate (PSS), 28) and AlN and high-Al-composition AlGaN epilayers on Si(111) substrates.…”