JPH04252019A - Growth method for hetroepitaxial crystal - Google Patents

Abstract

PURPOSE:To form a heterojunction which has the profile of a steep composition and whose heterojunction interface characteristic is good by using an MBE growth method regarding the formation method of the heterojunction constituted of two kinds of III-V compound semiconductors whose group element is different. CONSTITUTION:When a III1V1/III2V2 heterojunction is formed by an MBE method, the following are included sequentially: a process to stop a III1 beam; a process to radiate a V2 beam; a process to stop a V2 beam; and a process to radiate a III2 beam. The heterojunction is constituted of processes by which the following are set respectively: the time until the III2 beam is radiated from the stop of the III2 beam; the time until the III2 beam is radiated from the stop of the V1 beam; and the superposition time of the V1 beam on the V2 beam.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for forming a heterojunction composed of two types of III-V compound semiconductors containing different Group V elements, and in particular to a method for forming the heterojunction by a molecular beam epitaxial method (MBE method). Regarding the forming method.

In recent years, the development of devices using compound semiconductor heterojunctions has been active. In particular, when forming a heterojunction system containing different group V elements, such as InAs/GaSb, by the MBE growth method, it is necessary to switch the group V element beam at the same time as switching the group III element beam. If this beam switching is not performed appropriately, it will not be possible to obtain the desired heterojunction interface characteristics based on the ideally steep composition profile. That is, when forming such a type of heterojunction using the MBE growth method, the beam switching method controls the heterojunction interface characteristics.

0003

[Prior Art] Conventionally, when forming a heterojunction of III-V compound semiconductors containing different group V elements by the MBE method, first the group III element beam and the group V element beam used to grow the semiconductor on one side of the junction are Beam switching was performed in which the element beams were stopped at the same time, and then the group III element beam and the group V element beam were simultaneously started to be emitted to grow the semiconductor on the other side of the junction.

0004

[Problem to be solved by the invention] However, in such a method, in reality, the component elements of the semiconductor to be grown first and the component elements of the semiconductor to be grown next may mix at some point. , Therefore in this case,
Because mixed crystals of these mixed components are formed, there is a problem in that it is not possible to obtain a bonding interface with a steep composition. This was also a problem in that it was not possible to obtain the desired heterojunction interface properties.

[0005] Accordingly, an object of the present invention is to form a heterojunction having a steep composition profile and good heterojunction interface characteristics using the MBE growth method.

[0006]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. In the following, III 1 V1 is first grown by the MBE method, and then III 2 V1 is grown.
Grow V2, III 1 V1/III
The case of forming a 2V2 heterojunction will be explained. The III 1 beam is stopped to terminate the growth of III 1 V1. However, the V1 beam will continue for a while. After an appropriate time, the V2 beam is started, and after an appropriate time, the V1 beam is stopped. In Figure 1, the transient state caused by the high vapor pressure of group V elements is omitted. The III 2 beam is started t hours after V1 is stopped. From this point on, growth of III 2 V2 begins. The starting point of the beam of III 2 is III 1
This is T hours after the beam stops.

[0007] In such a growth method, the above problems are solved by selecting appropriate values of t and T.

[0008]

[Operation] When a III-V compound semiconductor is grown by the MBE growth method, the growth is controlled by a group III element beam. That is, MBE growth does not occur unless the substrate is exposed to a group V element atmosphere and is not irradiated with a group III element beam. Utilizing this effect, we can calculate the time (T
), that is, the group V element beam is switched within the growth interruption time. By doing this, each element will not be mixed, and V1 will be mixed into III 2 V2 to form 3 such as III 2 V2 V1.
Inclusion of the original compound does not occur. Therefore,
A bond with a steep composition profile is obtained. However, if the growth interruption time (T) is too long, impurities in the residual gas will be adsorbed onto the growth surface, which is expected to deteriorate the interfacial properties. Figure 2 shows the effect of growth interruption time (T) on heterojunction interface properties.
It is a graph showing experimental data investigated by the mobility of dimensional electron gas. The experiment was carried out using the best known Ga
Although this study was carried out on an As/AlGaAs heterojunction interface, it is common in investigating the influence of the growth interruption time (T) on the heterojunction interface properties, so generality is not lost. do not have. The method for forming this heterojunction is as follows. First, GaAs M
After performing BE, G while maintaining the As beam.
Stop the a-beam. After T time, Ga beam and Al beam are started simultaneously to grow AlGaAs. A two-dimensional electron gas is generated on the GaAs side of this heterojunction, and the mobility of this electron is 7
Measured at 7K. In the experiment, T is 0 minutes,
It was performed on three types of heterojunctions: 3 minutes and 6 minutes. As can be seen from the graph in Figure 2, T is 5
If the amount exceeds 100%, the mobility deteriorates significantly. Therefore, T must be shorter than 5 minutes to prevent deterioration of the bonding interface properties.

[0009] When the V group elements are different, such as V1 and V2, the influence of V1 remaining in the background appears even after switching from V1 to V2.
However, generally the background level is 2
Since it is about an order of magnitude smaller, the concentration of V1 in terms of crystal composition is less than 1%. Therefore, although the effect is small when such a heterojunction is used in high-speed devices, it cannot be ignored for special applications. Therefore, it has been confirmed that in order to prevent such V1 contamination, it is sufficient if the time t from the stop of V1 until the start of the III 2 beam is several seconds to 2 minutes.

0010

[Embodiments] Two embodiments of the present invention will be explained with reference to the drawings. First embodiment Figure 3 (a) shows the configuration diagram of the first embodiment.
(b) shows the time chart for its production. The MBE substrate is made of semi-insulating GaAs (SI-GaAs).
), and i-AlSb, i-InAs,
i-AlGaSb is sequentially formed. First, i
- Stop the Al beam after growing 1 μm of AlSb. This time is set to 0, and the As beam starts to be emitted after 1 second, and the Sb beam is stopped after 2 seconds. Next, at time 121 seconds, injection of the In beam is started, and the growth of i-InAs is started. i-In
The In beam is stopped when As has grown to a thickness of 20 nm. If this time is set to 0 again, 1
The Sb beam starts to be emitted after a second, and the As beam stops after two seconds. 60 seconds after the start of Sb beam injection,
i-A by starting injection of Al beam and Ga beam at the same time
Grow 50 nm of lGaSb. Second Embodiment FIG. 4(a) shows a configuration diagram of the second embodiment, and FIG. 4(b) shows a time chart for its manufacture. i-AlSb, i on SI-InP substrate
-GaSb, i-InAs, and i-AlSb are formed in sequence. In addition, this time chart shows i-GaSb, i-InAs,
Only the parts related to i-AlSb fabrication are shown. First, i-AlSb is grown to 1 μm, and then i-GaSb is grown to 30 nm. At that point, first, only the Ga beam is stopped. This time is set as 0, and the As beam is started to be emitted after 1 second. Stop the Sb beam after 2 seconds. After emitting the As beam for 2 minutes, start injecting the In beam. This allows InAs to grow to 30 nm, at which point I
Stop the n beam. Assuming this time as 0, 1
The Sb beam is started to be emitted after 2 seconds, and the As beam is stopped after 2 seconds. After 61 seconds, the Al beam is started to be emitted to grow 20 nm of i-AlSb.

[0011]

[Effects of the Invention] As described above, in the present invention, when forming III-V compound semiconductor heterojunctions containing different group V elements, by appropriately setting switching time programs for group III and group V elements, different Two types of V
The ternary compound semiconductor produced by the mixing of metal elements is not mixed in the vicinity of the heterojunction, and contamination of the vicinity of the heterojunction by residual impurities can also be avoided, resulting in good heterojunction characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a diagram showing the influence of growth interruption time on heterojunction interface characteristics in the present invention.

FIG. 3 is a diagram showing a configuration diagram and a time chart in the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration diagram and a time chart in a second embodiment of the present invention.

Claims (1)

[Claims] [Claim 1] Two types of III- with different group V elements
Heterojunction II composed of group V compound semiconductors
In the I 1 V1 / III 2 V2 crystal growth method, first, after stopping the III 1 beam,
A crystal growth method characterized in that the III 2 beam is emitted after a predetermined period of time during which impurities are not substantially adsorbed on the growth surface, and the V1 beam is stopped and the V2 beam is started to be ejected during the predetermined period of time. 2. The crystal growth method according to claim 1, further comprising a period in which the V1 beam and the V2 beam overlap.