Vapor phase epitaxy method

Abstract

A vapor phase epitaxy method including: providing a III-V substrate of a first conductivity type, introducing the III-V substrate into a reaction chamber of a vapor phase epitaxy system at a loading temperature, heating the III-V substrate from the loading temperature to an epitaxy temperature while introducing an initial gas flow, depositing a III-V layer with a dopant concentration of a dopant of the first conductivity type on a surface of the III-V substrate from the vapor phase from an epitaxial gas flow, fed into the reaction chamber and comprising the carrier gas, the first precursor, and at least one second precursor for an element of main group III, wherein during the heating from the loading temperature to the epitaxy temperature, a third precursor for a dopant of the first conductivity type is added to the initial gas flow.

Claims

1. A vapor phase epitaxy method comprising: providing a III-V substrate of a first conductivity type; introducing the III-V substrate into a reaction chamber of a vapor phase epitaxy system at a loading temperature; heating the III-V substrate from the loading temperature to an epitaxy temperature while introducing an initial gas flow comprising a carrier gas and a first precursor for a first element from main group V; depositing a III-V layer with a dopant concentration of a dopant of the first conductivity type on a surface of the III-V substrate from the vapor phase from an epitaxial gas flow, fed into the reaction chamber and comprising the carrier gas, the first precursor, and at least one second precursor for an element of main group III; and adding, during the heating from the loading temperature to the epitaxy temperature, a third precursor for a dopant of the first conductivity type to the initial gas flow.

2. The vapor phase epitaxy method according to claim 1, wherein the addition of the third precursor begins during the heating below a temperature of 500° C. or below a temperature of 400° C. or below a temperature of 300° C.

3. The vapor phase epitaxy method according to claim 1, wherein a total mass flow of the initial gas flow is at most 10% of a total mass flow of the epitaxial gas flow.

4. The vapor phase epitaxy method according to claim 1, wherein a planetary reactor is used as the reaction chamber.

5. The vapor phase epitaxy method according to claim 1, wherein a III-V substrate with a dopant concentration of at least 1.Math.10.sup.17 cm.sup.−3 or at least 1.Math.10.sup.18 cm.sup.−3 is provided.

6. The vapor phase epitaxy method according to claim 1, wherein the III-V layer is grown with a dopant concentration decreasing from 10.sup.17 cm.sup.−3 to 10.sup.15 cm.sup.−3.

7. The vapor phase epitaxy method according to claim 1, wherein the III-V layer is grown with a layer thickness of at most 30 μm.

8. The vapor phase epitaxy method according to claim 1, wherein the first conductivity type is p or n.

9. The vapor phase epitaxy method according to claim 1, wherein the III-V layer is grown firmly bonded on the surface of the III-V substrate.

10. The vapor phase epitaxy method according to claim 1, wherein the dopant concentration within the III-V layer is set by a ratio of a mass flow of the first precursor to a mass flow of the second precursor and/or by a mass flow, added to the epitaxial gas flow, of the third precursor.

11. The vapor phase epitaxy method according to claim 1, wherein the third precursor is dimethylzinc or diethylzinc or carbon tetrabromide or 1,2-bis(cyclopentadienyl)magnesium or monosilane or disilane or dimethyl telluride or diethyl telluride or diisopropyl telluride.

12. The vapor phase epitaxy method according to claim 1, wherein the III-V substrate has a constant dopant concentration over a layer thickness or a dopant concentration that changes by at most 1%.

13. The vapor phase epitaxy method according to claim 1, wherein the III-V substrate comprises or consists of GaAs.

14. The vapor phase epitaxy method according to claim 1, wherein the epitaxy temperature is at least 550° C. or at least 600° C. and at most 900° C.

15. The vapor phase epitaxy method according to claim 1, wherein the addition of the third precursor begins during the heating starting from a temperature of at least 150° C. or at least starting from a temperature of 200° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows a plan view of substrates arranged in a reaction chamber during a heating process;

(3) FIG. 2 shows a temperature profile of a first embodiment of the invention of a heating process;

(4) FIG. 3 shows a dopant concentration profile over a III-V substrate and a subsequent III-V layer; and

(5) FIG. 4 shows profiles of characteristic curves.

DETAILED DESCRIPTION

(6) The illustration in FIG. 1 shows a sectional view from above of a reactor chamber K, designed as a planetary reactor, of a vapor phase epitaxy system A with a number of III-V substrates arranged therein and a gas inlet member O through which an epitaxial gas flow is introduced into the reactor chamber K to deposit a III-V layer.

(7) The epitaxial gas flow has at least one carrier gas, a first precursor for an element of main group V, and a second precursor for an element of main group III.

(8) After reactor chamber K is loaded at a loading temperature T.sub.B, the reactor chamber is closed, pumped out, and heated.

(9) During the heating of the reactor chamber, an initial gas flow I is fed into reactor chamber K through gas inlet member O.

(10) The heating follows, for example, the temperature profile shown in the illustration in FIG. 2, wherein the initial gas flow I at a point in time t0 at the loading temperature T.sub.B comprises the carrier gas and a first precursor for an element of main group V.

(11) A third precursor for a dopant of the first conductivity type is added to the initial gas flow starting when a trigger temperature T.sub.T is reached at a point in time t2 and until an epitaxy temperature T.sub.E is reached.

(12) It is understood that the trigger temperature T.sub.T is less than the epitaxy temperature T.sub.E and time t.sub.2 lies before time t.sub.3. The trigger temperature T.sub.T is, for example, 500° C. or 400° C.

(13) Alternatively, the trigger temperature T.sub.T corresponds to the loading temperature T.sub.B, so that the third precursor is already present in the initial gas flow I from the point in time t.sub.2-t.sub.0, therefore, from the beginning.

(14) It should be noted for the sake of completeness that a gas flow prior to loading is not possible in terms of safety.

(15) The illustration in FIG. 3 shows a profile of a dopant concentration of the first conductivity type D over a thickness d of the III-V substrate and the III-V layer. The III-V substrate provided has a constant dopant concentration D.sub.SUB of the first conductivity type over a thickness d.sub.SUB.

(16) By adding the third precursor during the heating, the doping of the III-V layer grown on the III-V substrate S begins directly following the III-V substrate S with a dopant concentration D.sub.max of the first conductivity type. The dopant concentration decreases up to a dopant concentration D.sub.min over a layer thickness d.sub.L of the III-V layer.

(17) Due to the dopant concentration profile achieved by the method of the invention, a diode characteristic following the ideal profile results for a component (diode) supplemented by a layer of the second conductivity type in the forward direction; this is shown by way of example as a solid line in the illustration in FIG. 4.

(18) Without the addition of the third precursor during heating, a thin undesirable layer, i.e., an intermediate layer, of the second conductivity type can form possibly between the substrate of the first conductivity type and the layer of the first conductivity type grown in the subsequent deposition step.

(19) Such a layer of the second conductivity type for a component (diode) supplemented by a further layer of the second conductivity type results in an extended blocking in the forward direction and a corresponding returning characteristic curve, as illustrated by the profile represented by crosses in the figure in FIG. 4.

(20) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.