Systematic study of epitaxy growth uniformity in a specific MOCVD reactor

Abstract

Gallium nitride (GaN) is a direct bandgap semiconductor widely used in bright light‐emitting diodes (LEDs). Thin‐film GaN is grown by metal‐organic chemical vapour deposition (MOCVD) technique. Reliability, efficiency and durability of LEDs are influenced critically by the quality of GaN films. In this report, a systematic study has been performed to investigate and optimize the growth process. Fluid flow, heat transfer and chemical reactions are calculated for a specific close‐coupled showerhead (CCS) MOCVD reactor. Influences of reactor dimensions and growth parameters have been examined after introducing the new conceptions of growth uniformity and growth efficiency. It is found that GaN growth rate is mainly affected by the concentration of (CH3)3Ga:NH3 on the susceptor, while growth uniformity is mainly influenced by the recirculating flows above the susceptor caused by natural convection. Effect of gas inlet temperature and the susceptor temperature over the growth rate can be explained by two competing mechanisms. High growth efficiency can be achieved by optimizing the reactor design.

Numerical Analysis of the High Pressure MOVPE Upside-Down Reactor for GaN Growth

“…Furthermore, the temperature measurements in the reactor chamber are limited due to the restricted access and the expected range (e.g., 600 • C to 1200 • C in the case of GaN). As a consequence, numerical simulations of the process [14][15][16][17][18] are necessary to predict and investigate the growth conditions, and to improve the epitaxy process.…”

“…Subsequent studies focused on specific apparatus constructions from small laboratory size solutions, suitable for processing 3 in wafers [17,[20][21][22][23][24][25] up to big, rotating disk or planetary constructions designed for more than 40 2-in substrates [15,[26][27][28][29][30]. The researchers investigated the geometry and shape of reactor chambers [15,25,27] with special emphasis placed on the distance between the inlet and the susceptor, the gas injection systems [22,26,31,32] responsible for proper chemical species delivery, as well as the operating parameters of the growth process [15,16,29,33].…”

Uniformity investigation of MOCVD‐grown LED layers

“…To deliver the market demands and to compete in the interests, in past decades equipment manufacturers have proposed some excellent MOCVD reactors for thin film fabrication, for example, the planetary reactors , the close‐coupled showerhead (CCS) reactors , and the high‐speed rotating disk reactors (RDR) . The epitaxial process is characterized by complex heat and mass transfers as well as by complicated chemical reactions , leading to difficulties in control of the growth parameters or conditions for perfect crystalline layers.…”

“…The film thickness uniformity is attributed to nitride deposition rate, and the wavelength and intensity uniformities are related to the quality of quantum wells and crystal perfections. Researchers have paid much attention to predict the deposition rate and its effect on the growth uniformity . Reactor designs and growth conditions play a role in temperature and species distributions in the reactor, thus influencing surface reactions on the substrates.…”

“…It has been reported that recirculating flow above the susceptor caused by complex thermal boundary conditions affects growth uniformity significantly. Increase of the gas‐inlet size and inlet‐gas velocity, and decrease of the distance between the gas inlet and the susceptor are beneficial for the growth uniformity . Meanwhile, the deposition rate is also dramatically dependent on the susceptor temperature by two competing mechanisms.…”