JP2725334B2 - 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 the 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 electron affinity of the semiconductor [Physics. Of Semiconductor Devices (Physics of
Semiconductor Devices, 1969, John Wiley R. Sons, I
nc.)]. 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
s. Rev. Lett.) Volume 22, 1969, p. 1433].

(Problems to be Solved by the Invention) The height of the Schottky barrier is preferably higher in order to improve rectification characteristics, and lower in order to reduce 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 provides a Schottky junction structure formed by an arbitrary metal and an n-type III-V compound semiconductor.
By doping a rare earth metal into the surface layer of the III-V compound semiconductor at a donor concentration of the II-V compound semiconductor or less, a Schottky junction structure with a high barrier height is realized. Further, in a Schottky junction structure formed by an arbitrary metal and a p-type III-V compound semiconductor, a rare earth metal is added to the surface layer of the III-V compound semiconductor.
A Schottky junction structure having a low barrier height is realized by doping at an acceptor concentration of the group V compound semiconductor or lower, and a Schottky barrier having a high barrier height is realized by doping a rare earth metal at a higher concentration than the acceptor concentration. This realizes a joining structure.

(Operation) For example, to increase the height of the Schottky barrier of an n-type semiconductor, it is sufficient to form a p ⁺ layer on the semiconductor surface, and to reduce this height, an n ⁺ -type layer is formed on the semiconductor surface. [Journal of Applied Physics (J. Appl. Phys.) Vol. 61, No. 51]
59]. However, when the n ⁺ and p ⁺ layers are formed on the surface in this way, the reverse bias withstand voltage is reduced, which is a serious problem in practical device application. Therefore, the present inventor, instead of doping the donor type and the acceptor type dopant, II
It has been conceived to dope an inactive rare earth metal in an IV 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
It has been shown to be controllable over a width of 250 meV. Barrier in Yb doping amount of the donor concentration (about 10 ¹⁷ cm ^-3 (less GaAs height 120meV also higher as compared to normal Al / GaAs Schottky barrier, the Yb doping amount 10 ¹⁷
The barrier height decreases as the doping amount increases with an increase of cm ^-3 or more, and at a doping amount of 10 ²¹ cm ^-3 , the barrier height becomes 130 meV lower than that of a normal Al / GaAs 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. Accordingly, it is possible to control the Schottky barrier also for the p-type III-V compound semiconductor, and the effect is to change the barrier height in the opposite direction to the effect for the n-type.

(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 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 the molecular beam epitaxy method. 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. In addition, the reverse bias withstand voltage was higher by 5 V than the place where Dy was not 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, n-type GaAs 5000Å doped with a Si concentration of 6 × 10 ¹⁶ cm ^-3 was grown on a cleaned n-type GaAs (001) substrate by the molecular beam epitaxial growth method. ²⁰ 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 0.56 eV, which is 200meV lower than the case without Sm doping.
Was obtained. In addition, the reverse bias withstand voltage was 6 V higher than that obtained when no Sm was doped.

(Embodiment 3) Dy is applied to the surface of a p-type GaAs semiconductor at a depth of 300 ° and 10 ¹⁷ 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 than in the case where Dy was not doped. In the experiment, p-type GaAs 5000Å doped with a Be concentration of 2 × 10 ¹⁷ cm ^-3 was grown on a cleaned p-type GaAs (001) substrate by molecular beam epitaxy, and Dy was further increased by 10 ¹⁷ over the surface layer 200Å. cm ^-3 doping. Then, Al was deposited at room temperature at 1000Å. Attach an electrode to the prepared sample
Evaluation was made by -V measurement and CV measurement to determine the Schottky barrier height and the reverse bias withstand voltage. As a result, the barrier height was obtained as 0.53 eV, which is 140 meV lower than the case without Dy doping. In addition, the reverse bias withstand voltage was higher by 5 V than when no Dy was doped.

(Example 4) p-type GaAs semiconductor surface for a depth 100Å to Sm 10 ²⁰ 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 Sm doping. In the experiment, p-type GaAs 5000Å doped with a Be concentration of 6 × 10 ¹⁶ cm ^-3 was grown on a cleaned p-type GaAs (001) substrate by the molecular beam epitaxial growth method. ²⁰ 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 0.87 eV, which is 200 meV lower than when no Sm is doped.
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 it grew by other growth methods
The same effect can be obtained even when the rare-earth metal is doped into the III-V compound semiconductor surface layer by diffusion or ion implantation. Further, the III-V semiconductor is not limited to GaAs, but may be InP, InGaAs, InG, or the like.
Applicable to aP etc. 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, I
The effects of the invention can be obtained even with alloys such as n, Ti, Y, Na, Ni, Co, Fe, Cr, Mn, Sb, V, W, and WSi.

(Effects of the Invention) As described above, the present invention can be applied to any metal and III-V
In the Schottky junction structure by the group III compound semiconductor,
By doping the III-V compound semiconductor surface layer with a rare earth metal, 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 (3)

(57) [Claims] In a Schottky junction structure formed of an arbitrary metal and an n-type III-V compound semiconductor, a rare earth metal is contained in the III-V compound semiconductor surface layer.
A Schottky junction structure having a high barrier height, which is doped at a donor concentration of II-V compound semiconductor or less. 2. In a Schottky junction structure formed by an arbitrary metal and a p-type III-V compound semiconductor, a rare earth metal is contained in the III-V compound semiconductor surface layer by the I-type compound.
A Schottky junction structure having a low barrier height, wherein the Schottky junction structure is doped at an acceptor concentration of a II-V compound semiconductor or lower. 3. In a Schottky junction structure formed by an arbitrary metal and a p-type III-V compound semiconductor, a rare earth metal is contained in the III-V compound semiconductor surface layer.
A Schottky junction structure having a high barrier height, which is doped at a concentration higher than the acceptor concentration of a II-V compound semiconductor.