4.3 Group III Nitride LED Epitaxial Technology
47
4.3.4 HVPE Method
Hydride Vapor Phase Epitaxy (HVPE) HVPE is the earliest technology used to study
GaN thin films and plays an important role in the early development of nitrides. In
1969, Maruska et al. modified the GaAs hydride equipment to form a GaN single
crystal film by vapor deposition of GaCl and NH 3 on a sapphire substrate using a hotwall reaction chamber [18]. However, due to the difficulty in reducing background
carrier concentration and p-type doping, this technique was completely replaced by
MOVCD and MBE technology in the late 1980s. In recent years, HVPE technology
has once again attracted people’s attention due to its own characteristics, and has
become a new research topic.
HVPE method usually uses the reaction product among GaCl, metal Ga, and
HCl gas as the group III source, and NH 3 as the group V source for epitaxial GaN
material. The basic principle and process are as follows: in the low temperature
region of the growth chamber, HCl gas flows through the quartz tube and the metal
Ga in the boat reacts with it to form GaCl. GaCl and NH 3 flow to the substrate in the
high temperature region driven by carrier gas, respectively. They mixed and reacted
above the substrate, and a part of the generated GaN is deposited on the surface of
the substrate. The remaining portion is deposited on the wall of the reaction tube.
Unreacted NH 3 and HCl proceed and react at the outlet of the reaction tube to form
solid NH 4 Cl white powder.
The main reactions are as follows [19]:
Low temperature zone : Ga(l) + HCl(g) → GaCl(g) + H 2
(4.8)
High temperature zone (1050 °C):
GaCl(g) + NH 3 → GaN + HCl(g) + H 2
(4.9)
In addition, there are side reactions in the chamber:
NH 3 (g) + HCl(g) → NH 4 Cl(s)
(4.10)
GaCl(g) + 2HCl(g) → GaCl 3 (g) + H 2 (g)
(4.11)
HVPE growth systems generally consist of furnace bodies and reactors, gallium
boats and gas pipes, gas distribution systems, and exhaust.
The processing system consists of four parts. According to the structural characteristics of the reactor, the HVPE system can be divided into two types: horizontal
and vertical. The horizontal HVPE systems are used by Karl-Marx University and
AIXTRON, Germany, Wisconsin University, and Russian Soft-impact. The vertical
type has been used by the University of Lincoping in Sweden, the University of
Justus-Liiebig in Germany, and the MIT in the United States. Both methods have
their own advantages and disadvantages. The horizontal structure is relatively mature.
47
4.3.4 HVPE Method
Hydride Vapor Phase Epitaxy (HVPE) HVPE is the earliest technology used to study
GaN thin films and plays an important role in the early development of nitrides. In
1969, Maruska et al. modified the GaAs hydride equipment to form a GaN single
crystal film by vapor deposition of GaCl and NH 3 on a sapphire substrate using a hotwall reaction chamber [18]. However, due to the difficulty in reducing background
carrier concentration and p-type doping, this technique was completely replaced by
MOVCD and MBE technology in the late 1980s. In recent years, HVPE technology
has once again attracted people’s attention due to its own characteristics, and has
become a new research topic.
HVPE method usually uses the reaction product among GaCl, metal Ga, and
HCl gas as the group III source, and NH 3 as the group V source for epitaxial GaN
material. The basic principle and process are as follows: in the low temperature
region of the growth chamber, HCl gas flows through the quartz tube and the metal
Ga in the boat reacts with it to form GaCl. GaCl and NH 3 flow to the substrate in the
high temperature region driven by carrier gas, respectively. They mixed and reacted
above the substrate, and a part of the generated GaN is deposited on the surface of
the substrate. The remaining portion is deposited on the wall of the reaction tube.
Unreacted NH 3 and HCl proceed and react at the outlet of the reaction tube to form
solid NH 4 Cl white powder.
The main reactions are as follows [19]:
Low temperature zone : Ga(l) + HCl(g) → GaCl(g) + H 2
(4.8)
High temperature zone (1050 °C):
GaCl(g) + NH 3 → GaN + HCl(g) + H 2
(4.9)
In addition, there are side reactions in the chamber:
NH 3 (g) + HCl(g) → NH 4 Cl(s)
(4.10)
GaCl(g) + 2HCl(g) → GaCl 3 (g) + H 2 (g)
(4.11)
HVPE growth systems generally consist of furnace bodies and reactors, gallium
boats and gas pipes, gas distribution systems, and exhaust.
The processing system consists of four parts. According to the structural characteristics of the reactor, the HVPE system can be divided into two types: horizontal
and vertical. The horizontal HVPE systems are used by Karl-Marx University and
AIXTRON, Germany, Wisconsin University, and Russian Soft-impact. The vertical
type has been used by the University of Lincoping in Sweden, the University of
Justus-Liiebig in Germany, and the MIT in the United States. Both methods have
their own advantages and disadvantages. The horizontal structure is relatively mature.