JP2576524B2 - Vapor growth method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth method, and more particularly to a method of vapor phase growing a compound semiconductor layer such as AlInAs or GaInAs lattice-matched on an InP substrate.

[Summary of the Invention]

The present invention provides a vapor growth method of a compound semiconductor layer on an InP substrate, a growth temperature higher before growing in PH ₃ atmosphere, 3
After performing a heat treatment of 0 minute or more on the InP substrate, the vapor phase growth of the compound semiconductor layer is started to reduce or eliminate the carriers present at the interface between the InP substrate and the vapor phase growth layer. Things.

[Conventional technology]

Research on crystal growth of mixed crystals such as AlInAs and GaInAs on InP substrates has been conducted by MOCVD (metal organic chemical vapor deposition), MBE (molecular beam epitaxy), CBE (chemical beam epitaxy), and the like.

In the MOCVD method using an organic metal as a raw material for a group III element, a hydride such as AsH ₃ or PH ₃ is generally used as a raw material for a group V element.

Mixed crystals such as AlxIn ₁ -xAs and GaxIn ₁ -xAs can be lattice-matched to InP by controlling the mixed crystal ratio. MOC
When growing a mixed crystal of AlInAs, GaInAs, etc. lattice-matched on an InP substrate by the VD method, dissociation of the group V element with a high vapor pressure from the substrate during the heating of the substrate until the InP substrate reaches a predetermined growth temperature To prevent this, it is necessary to apply phosphorous pressure.
Thus, for example, when the epitaxial growth of GaAs-based with GaAs substrates, as well as supplying AsH ₃ when heating the GaAs substrate, phosphorus InP substrate by supplying the reaction tube PH ₃ is hydride when InP substrate heating A method of applying pressure is generally used. Conventionally, after the InP substrate is kept at a predetermined growth temperature (for example, after a few minutes), supply of PH ₃ is stopped, and AsH ₃ and a desired organometallic gas are supplied to the reaction tube. Therefore, the growth of mixed crystals of AlInAs, GaInAs, etc. on the InP substrate was started.

[Problems to be solved by the invention]

When the electrical conductivity of the above-obtained lattice-matched or crystal-matched mixed crystal obtained by the above-described method is measured by the Hall measuring means, there is no report that n-type is obtained and p-type is obtained. (That is, in the case of an undoped mixed crystal, p-type and n-type could not be controlled only by controlling the V / III ratio.) For example, a 1 μm-thick epitaxial growth layer grown on the semi-insulating InP substrate (1) shown in FIG. (2) is gradually etched from the surface, and the hole measurement is repeated.
As shown in the figure, the carrier concentration with respect to the etching amount decreases with a slope corresponding to the volume concentration of the epitaxial growth layer, but n-type carriers remain even when the etching is performed near the interface between the epitaxial growth layer (2) and the InP substrate (1). Often observed.

The n-type carrier (3) present at this interface has an adverse effect on the evaluation of the characteristics of the growth layer (2) and cannot be evaluated correctly, or unfavorable electric conduction when fabricating a device structure such as an FET. There was an inconvenience such as that a pass was generated.

The present invention has been made in view of the above circumstances, and provides a vapor phase growth method capable of growing a compound half layer on an InP substrate so that n-type interface conduction is reduced or eliminated.

[Means for solving the problem]

The present invention, AlInAs lattice-matched to InP on an InP substrate by MOCVD, when the compound semiconductor layer such as GaInIs vapor phase growth, introducing PH ₃ before growth into the reaction tube, the PH ₃ atmosphere After performing a heat treatment on the InP substrate at a temperature equal to or higher than the vapor phase growth temperature for 30 minutes or more, the reaction gas is switched to start the vapor phase growth of the compound semiconductor layer.

[Action]

Before the growth, the InP substrate is subjected to a heat treatment at a temperature equal to or higher than the vapor phase growth temperature for 30 minutes or more in a PH ₃ atmosphere, and then the vapor phase growth is started, so that the interface between the compound semiconductor layer and the InP substrate. In this case, the n-type conduction conventionally observed is reduced or eliminated.

〔Example〕

A case where an undoped GaInAs layer (4) having a thickness of 1 μm is epitaxially grown on a semi-insulating InP substrate (1) by MOCVD as shown in FIG. 2 will be described.

An InP substrate (1) is placed on the susceptor in the reaction tube, and 20% hydrogen-based PH ₃ (flow rate 400 cc / min) is placed in the reaction tube before growth.
And H ₂ gas (flow rate 12 / min) as carrier gas every second
Supply at a flow rate of 1m. The pressure was normal pressure.

Then, the InP substrate (1) is heated, and the substrate temperature is maintained at a vapor phase growth temperature of 640 ° C., and this state is maintained for a predetermined period of time.
The supply of H ₃ is stopped, the gas is switched, and a reaction gas of AsH ₃ , TMG (trimethyl potassium) and TMI (trimethyl indium) is supplied into the reaction tube together with the carrier gas, and the growth of the undoped GaInAs layer (4) is started.

FIG. 1 shows the processing time when the InP substrate (1) was heat-treated in a PH ₃ atmosphere before growth, that is, the InP substrate (1) was grown at a growth temperature of 6 ° C.
FIG. 7 is a graph showing a change in sheet carrier concentration No at an epitaxial growth layer (undoped GaInAs layer) -InP substrate interface (5) with respect to a holding time after being heated to 40 ° C. FIG. In the figure, curve (I) shows the sheet carrier concentration, and curve (II) shows the substrate temperature of the InP substrate (1).

As is clear from FIG. 1, after the InP substrate (1) was maintained at the growth temperature of 640 ° C., the retention time (PH ₃ processing time) for keeping the InP substrate in the PH ₃ atmosphere was increased, and the interface was increased. The sheet carrier concentration No indicating the conduction in (5) tends to decrease. When the holding time is set to 30 minutes or more, the sheet carrier concentration can be extremely reduced or set to zero.

In the above example, the temperature of the InP substrate during the heat treatment before the growth was set to the growth temperature of 640 ° C.
As shown in II), the growth temperature may be maintained at, for example, 700 ° C. higher than the growth temperature, and the growth temperature may be set to 640 ° C. during growth, or the curve (I
As shown in V), the first half of the heat treatment may be, for example, 700 ° C., and the second half may be maintained at the growth temperature of 640 ° C.

〔The invention's effect〕

According to the present invention, the epitaxial growth layer-InP substrate is subjected to a heat treatment at a growth temperature or more in a PH ₃ atmosphere for 30 minutes or more before the growth, and thereafter, the gaseous growth is started by switching to a reaction gas. N-type conduction at the interface can be reduced or eliminated. Moreover, this can be performed without making any changes to the conventional MOCVD apparatus.

Therefore, if a compound semiconductor layer is vapor-phase grown on an InP substrate using this method, the characteristics of the grown layer can be correctly evaluated, and the electrical conductivity can be improved even when a device structure such as an FET is manufactured. No path occurs.

[Brief description of the drawings]

Graph showing the relationship between sheet carrier concentration and the PH ₃ processing time at the interface Figure 1 is for explaining the vapor growth method according to the invention, FIG. 2 is a cross-sectional view of the sample of the present embodiment, FIG. 3 is a conventional example Graph showing the change of the sheet carrier concentration n _S at each depth position of the epitaxial growth layer provided for the description,
FIG. 4 is a sectional view of the measurement sample of FIG. (1) InP substrate, (2) epitaxial growth layer,
(4) is an undoped GaInAs layer.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein said compound semiconductor layer is subjected to a heat treatment at a growth temperature of 30 ° C. or more in a PH ₃ atmosphere for growing said compound semiconductor layer on the InP substrate in a vapor phase.
After applying to an nP substrate, the vapor phase growth of the compound semiconductor layer is started.