JP2663515B2 - Schottky junction structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a Schottky junction structure in which a Schottky barrier height of a semiconductor can be controlled.

(Prior Art) The height of a Schottky barrier when a single metal is brought into contact with a semiconductor is ideally given by the difference between the work function of the metal and the power affinity of the semiconductor [Physics. Of Semiconductor Devices (Physics of S
emiconductor Devices, 1969, John Wiley R Sons, In
c.]. Therefore, in order to change the height of the Schottky barrier with respect to an arbitrary semiconductor, it is necessary to make contact with metals having different work functions. However, depending on the type of semiconductor, even when metals having different work functions are brought into contact with each other, the Fermi level is fixed (pinned) to a constant value, and it is impossible to change the height of the Schottky barrier.

III-V semiconductors with high industrial value were a prominent example [Physical Review Letters (Phy.
Rev. Lett.) Volume 22, 1969, p. 1433].

(Problems to be Solved by the Invention) The height of the Schottky barrier is preferably higher for improving, for example, rectification characteristics, and lower for lowering contact resistance. Furthermore, the height of the Schottky barrier is an important factor that determines the threshold voltage of a transistor. Therefore, as described above, the fact that the height of the Schottky barrier is uncontrollable in a group III-V compound semiconductor having a high utility value has been a great handicap in device design.

An object of the present invention is to provide a Schottky junction structure in which the height of a Schottky barrier of a semiconductor can be controlled.

(Means for Solving the Problems) The present invention is characterized in that, in a Schottky junction structure using an arbitrary metal and a III-V compound semiconductor, the surface layer of the III-V compound semiconductor is doped with a rare earth metal. To provide a Schottky junction structure.

(Operation) For example, to increase the Schottky barrier height of an n-type semiconductor, a p ⁺ layer may be formed on the semiconductor surface, and to reduce this height, an n ⁺ layer may be formed on the semiconductor surface. It is known that we should do it. [Journal of Aprado Physics (J. Appl. Psys.) Vol. 61, p. 5159]
However, when the n ⁺ and p ⁺ layers are formed on the surface as described above, the reverse bias withstand voltage is reduced, which is a serious problem in practical device application. Accordingly, the present inventor has proposed, instead of doping a donor-type or an acceptor-type dopant, III-
It has been considered to dope a rare earth metal that is electrically inactive in a group V compound semiconductor. Then, when the Schottky barrier against Al was obtained when Yb was doped into n-type GaAs over a surface depth of 100 ° while changing the concentration, there was a concentration dependency of the barrier height as shown in FIG. It has been found. Here, the barrier height of Al / n-GaAs is 250 m
It is shown to be controllable over a range of eV.
At a Yb doping amount below the GaAs donor concentration (about 10 ¹⁷ cm ^-3 ), the barrier height is 120 meV higher than that of a normal Al / GaAs Schottky barrier, and the Yb doping amount is 10 ¹⁷ cm ^-3.
With the above increase, the barrier height decreases with the doping amount, and at a doping amount of 10 ²¹ cm ^-3 , the normal Al / G
130meV lower than aAs Schottky barrier. Further, in all of these samples, the reverse bias withstand voltage was larger than that in the case where the rare earth metal was not doped.

Such effects were found when doping other rare earth metals in addition to Yb. Also other than GaAs
It was also found when doping III-V compound semiconductors. The reason why this effect appears is not necessarily clear, but it is considered that the Fermi level changes due to distortion or the like caused by doping.

(Example) Hereinafter, an example of the present invention will be described.

(Example 1) Dy is applied to the surface of an n-type GaAs semiconductor over a depth of 300 mm by 10 ¹⁷ c
When the Schottky barrier against Al with m- ³ doping was measured, a higher barrier height and a higher reverse bias withstand voltage were obtained than those without Dy doping. In this experiment, n-type GaAs 5000Å doped with a Si concentration of 2 × 10 ¹⁷ cm ^-3 was grown on a cleaned n-type GaAs (001) substrate by molecular beam epitaxy. 10 ¹⁷ cm ^-3 doping. Then, Al was deposited at room temperature at 1000Å. An electrode was attached to the manufactured sample, and the sample was evaluated by IV measurement and CV measurement to determine the Schottky barrier height and the reverse bias withstand voltage. As a result, the barrier height is 0.90 eV, which is 140 meV higher than when Dy is not doped.
Was obtained. Also, the reverse bias withstand voltage was higher by 5 V than when no Dy was doped.

(Example 2) Sm was applied to the surface of an n-type GaAs semiconductor over a depth of 100 mm to 10 ²⁰ c.
When the Schottky barrier against Al in the case of m ⁻³ doping was measured, a lower barrier height and a higher reverse bias withstand voltage were obtained as compared with the case where Sm was not doped.

In the experiment, 5000 nm of n-type GaAs doped with a Si concentration of 2 × 10 ¹⁷ cm ^-3 was grown on a cleaned n-type GaAs (001) substrate by molecular beam epitaxy, and at this time, the outermost surface layer was 100 mm.
Further, Sm was further doped with 10 ²⁰ cm ^-3 . Then, Al was deposited at room temperature at 1000Å. An electrode was attached to the manufactured sample, and the sample was evaluated by IV measurement and CV measurement to determine the Schottky barrier height and the reverse bias withstand voltage. as a result,
The barrier height is 200meV lower than when Sm is not doped.
A value of 56 eV was obtained. In addition, the reverse bias withstand voltage was 6 V higher than that obtained when no Sm was doped.

In this embodiment, the case where a sample is manufactured by molecular beam epitaxial growth is shown, but the effect of the present invention is not based on the growth method. Therefore, the same effect can be obtained even when the rare-earth metal is doped into the surface layer of the group III-V compound semiconductor grown by another growth method by diffusion or ion implantation. Further, the III-V group semiconductor is not limited to GaAs, but may be InP, InGaAs, or IGaAs.
Also applicable to nGaP and the like. Rare earth metals other than those used in the examples, such as Ce, Pr, Nd, Pm, Eu, Gd, Tb,
Ho, Er, Tm, Yb, Lu, etc. may be used. As the electrode metal, a metal other than Al that forms a Schottky junction such as Au,
Pd, Ag, Cu, Sn, In, Ti, Y, Na, Ni, Co, Fe, Cr, M
The effects of the present invention can be obtained even with alloys such as n, Sb, V, W, and WSi.

(Effects of the Invention) As described above, the present invention can be applied to any metal and III-V
By doping the III-V compound semiconductor surface layer with a rare earth metal in a Schottky junction structure using a group compound semiconductor, there is an effect of controlling the Schottky barrier height while having a high reverse bias withstand voltage.

[Brief description of the drawings]

FIG. 1 is a diagram showing the dependence of the height of a Schottky barrier on the concentration of a rare earth element according to an embodiment of the present invention.

Claims (1)

(57) [Claims] 1. A Schottky junction structure comprising an arbitrary metal and a group III-V compound semiconductor, wherein the surface layer of the group III-V compound semiconductor is doped with a rare earth metal.