JPS5846617A - Formation of compound semiconductor p-n junction - Google Patents

Abstract

PURPOSE:To preserve the impurity profile and to avoid damage to a crystal substrate by ion-implanting carbon atoms into a III-V group compound single crystal having the N type electric conduction characteristic and substituting most of the implanted carbon atoms for atoms on Vb group element lattice points by means of heat treatment. CONSTITUTION:An N type GaAs single crystal substrate 2 having a low electron density of about 10<14>cm<-3> is formed by epitaxial growth on an N type GaAs single crystal substrate 1, and carbon atoms are implanted with a density of 10<15>cm<-3> from the crystal orientation in which the channeling effect is avoidable to form a carbon-contained layer 3 having a carbon density of 10<18>-10<19>cm<-3> on the substrate 2. This is then annealed for a long time in a Ga solution to substitute most of the implanted carbon atoms for atoms on the As lattice points, thus forming a P type layer 5 and a P-N junction 4. As compared to the P-N junction formed by Zn diffusion or ion implantation this P-N junction has a precisely-controlled impurity profile and a low degree of damage, therefore, the efficiency of photoelectric conversion is improved, giving superior characteristics to an LED, a laser diode and an optical detector.

Description

[Detailed description of the invention] The present invention relates to a method for forming a compound semiconductor PNg composite.

In recent years, 1m-v group semiconductor crystals, especially gallium arsenide (
Ion implantation technology can be used to accurately control impurity profiles in single-crystal optical devices, such as light emitting diodes (LEDs), semiconductor laser diodes, and photodetectors, which can be achieved by diffusion or growth methods. There is a lot of interest in the technology for forming compound semiconductor PN junctions with unprecedentedly high performance. Furthermore, with the recent appearance of optoelectronic composite integrated devices that attempt to functionally form multiple electronic devices and optical devices on a single GaAs single crystal substrate, it is believed that the importance of such technology will further increase. It is being

Conventionally, in compound semiconductors, ion implantation technology has been used to
When forming an N junction, it has been common practice to implant O impurities such as Zn, Mg, or Be into a crystal substrate having an electrical conductivity of Nil. But in this zf
(i) is difficult to maintain the implantation profile as a result of re-diffusion during activation after implantation; and (9) 201Mg both have large atomic weights and damage the crystal substrate during implantation.

It usually causes a significant decrease in photoelectric properties such as energy consumption and photovoltaic force. On the other hand, B. is known to cause little damage due to its small atomic weight, but it has disadvantages such as being highly toxic and not easy to handle, so it is not generally used in practical devices. There wasn't. As described above, the conventional method has the disadvantage that it is difficult to form a PN junction while accurately preserving the impurity profile without damaging the compound semiconductor.

The present invention eliminates the above drawbacks and provides a method for forming a compound semiconductor PN junction that is easy to handle, accurately preserves the impurity profile, and causes very little damage to the crystal substrate.

A method for forming a compound semiconductor PN junction according to the present invention is as follows.

After ion-implanting carbon atoms at a density higher than KIO "Ca1-" on the surface of a single crystal of a Ca-V group compound having N-type electrical conductivity, it is carried out in a vacuum, in Group 1b metal vapor, or by forming a mold layer. Features.

Embodiments of the present invention will be described with reference to the drawings.

The figure is a cross-sectional view of a compound semiconductor for explaining one embodiment of the present invention.

On an N-type GaAs single crystal substrate with an electron density of 101613 or more I K 1014 am-'' Low electron density t4) On a crystal substrate on which a GmAm single crystal layer 2 of Nll is grown to a thickness of 3 μmK by epitaxial method K 200Ke
When carbon atoms are implanted at a density of 1615α-2 with an energy of V from a known crystal orientation that avoids channeling effects, carbon gold with a concentration of 1018 to 10 cm-2 from a depth of 0.5 μm to the surface is obtained. Layer 3 is formed. As is well known.

Carbon atoms are amphoteric impurities in QaA crystals, and can act as either donors or acceptors by appropriate activation; under the usual 8i3N4 coating, or under A, H,
Instead of activation by annealing in an atmosphere, it is necessary to perform annealing in a vacuum, Ga vapor, or Ga melt. Examples of experimental results show that most of the implanted carbon atoms can be replaced with As lattice points by annealing in a Ga melt for 1 hour or more at a temperature of 10,000 ℃ or less. A P-type layer 5 and a PN junction 4 are formed. The impurity profile of the GaAm crystal PN junction formed in this manner is more accurately controlled than that obtained by Zn diffusion or ion implantation.

Moreover, since the degree of damage is extremely low, it has excellent luminous efficiency or photoelectric conversion efficiency, and provides excellent characteristics when manufacturing IJD% laser diodes and photodetectors.

In order to replace the implanted carbon atoms at the As lattice sites, it is necessary to perform annealing in vacuum, gallium vapor, or gallium melt as described above. In order to carry out the activation effectively at a high temperature of .degree. C. or higher, it is advantageous to use the Ga melt. A temperature of 1000° C. or higher is not advantageous because it causes decomposition of the GaAm crystal.

Before depositing a thin film cap layer such as 8isN4 or annealing in AsH1, most of the carbon atoms are replaced by Ga lattice points and no PN junction is formed. Note that carbon atoms can be converted to Ga depending on the diffusion method or growth method.
It is already known that it is not easy to introduce Am into a crystal at a high concentration and activate it, but a method that combines ion implantation and an appropriate annealing method can obtain sufficient conductivity for both Pg and N types. It's almost the only way. In addition, in order to obtain a sufficiently low sheet resistance, it is necessary to implant carbon atoms at a concentration of 10" cm or more. Although the above example is for GaAs, the present invention is not limited to this. -V group compounds such as GmP and InP, GaA? According to the present invention, as described in detail above, IV of As, InGaAsP, etc.

This is highly effective because it provides a method for forming a compound semiconductor PN junction in which the impurity profile is accurately preserved and damage to the crystal substrate is extremely small.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a compound semiconductor for explaining one embodiment of the present invention. l... NWGaAs single crystal substrate, 2...
-N WGaAs single crystal layer, 3...carbon-containing layer, 4...PN junction.

Claims (1)

[Claims] After implanting carbon atoms at a concentration of 901018 or more l tyn into the surface of a single crystal of a ■-■ group compound having N-type electrical conductivity characteristics by iono-implantation. In a vacuum. (2) A method for forming a compound semiconductor PN junction, which is characterized in that it is formed in a group b metal atmosphere or by molten 11b.