FR2582023A1 - METHOD FOR DEVELOPING A FILM OF A MONOCRYSTAL GAAS IN THE FORM OF A SINGLE MOLECULAR LAYER - Google Patents

Abstract

A. DEVELOPMENT PROCESS OF A FILM FROM A MONOCRISTAL GAAS, IN THE FORM OF A SINGLE MOLECULAR LAYER. B.PROCEDE CHARACTERIZED IN THAT THE VACUUM IS ESTABLISHED INSIDE THE DEVELOPMENT TANK 1 AT A PREDETERMINED PRESSURE; THE TEG TRIETHYLGALLIUM 8 GAS IS INTRODUCED INTO THIS DEVELOPMENT TANK 1 UNDER A PREDETERMINED PRESSURE FOR A PREDETERMINED TIME, AND AFTER THE EVACUATION OF THE TEG GAS, THE ASH (ARSINE) 9 GAS IS INTRODUCED IN THIS PREDERMINED DEVELOPMENT TANK UNDER A PRESSURE PENDING PREDETERMINED TIME AND THE CYCLE IS REPEATED TO DEVELOP AT LEAST PRACTICE A MOLECULAR LAYER TO FORM A FILM OF A MONOCRISTAL GAAS OF THE THICKNESS DESIRED TO THE PRECISION OF A MOLECULAR LAYER. C. THE INVENTION RELATES TO A PROCESS FOR DEVELOPING A FILM FROM A GAAS MONOCRISTAL IN THE FORM OF A SINGLE MOLECULAR LAYER.

Description

Process for developing a GaAs single crystal film

  in the form of a single molecular layer. "

  The present invention relates to a method of developing a monocrystal GaAs film for forming a GaAs single crystal developing layer in the form of a single molecular layer.

Description of the prior art:

It is known as an epi

  gas phase taxonomy for the production of a film

  of a semiconductor crystal, a process for developing

  gas phase of an organic metal (hereinafter referred to as

  after "MO-CVD process") as well as an epitaxial process

  molecular beam (hereinafter referred to as "MBE process").

  However, when a compound semiconductor is produced

  between group III and group V such as GaAs by the

  yielding MO-CVD, group III elements, group V elements are used as sources, the carrier gas being hydrogen; these elements are introduced simultaneously to develop by thermal cracking, so that the layer thus developed is of poor quality. We

  has the further disadvantage that the order of the molecular layer

  simple eyepiece is difficult to adjust.

  Moreover, the MBE process, well

  known as a method of developing a useful crystal

  reads an extremely high vacuum with physical adsorption as a first step, so that the quality of the crystal obtained is lower than that of the crystal resulting from the gas phase development process using a

  chemical reaction. When developing a semi-compound

  between group III and group V such as GaAs, Group III elements and Group V elements are used as sources, the source itself being placed in a development chamber. As a result, the setting of the emitted gas obtained by heating the

  the source and the quantity vaporized as well as the

  the source are difficult and difficult

  to maintain constant the speed of development

  for an extended period. In addition, a

  valiant vacuum to provide vaporized material is complicated. In addition, it is difficult to

  precisely the stoichiometry of the semi-compound

  driver and furthermore has the disadvantage of

  to be able to obtain a crystal of high quality.

  Taking into account the above, the present inventors have previously proposed a method of developing a semiconductor crystal for controlling the growth of the film-like layer constituting the single molecular layer (see FIG.

  Japanese Patent Applications 153977/1984 and 153978/1984).

  These documents will be explained using Figure 5.

  According to FIG. 5, reference numeral 1 denotes a development reservoir which is made of metal, for example made of stainless steel 2, a gate valve 3, an outlet chamber for producing a very high vacuum in the development chamber 1;

  nozzles 4, 5 for introducing the gaseous compounds

  components of group III and group V elements or III and V group III semiconductor compounds, for example; the valves 6, 7 serve to open and close the nozzles 4, 5_; 8 denotes a gaseous compound containing a group III element; the

  reference 9 designates a gaseous compound containing an element

  group V; 10 denotes a heating device for heating the base and which is a tungsten wire (W) on which is sealed a glass of guartz,

  the cable or the like not shown. The numerical reference

  11 designates a thermocouple for measuring the temperature

  erasure; reference 12 designates a carrier for a compound semiconductor; reference 13 designates a pressure gauge for measuring the degree of vacuum in the

growth reservoir.

  The process of epitaxial growth of GaAs molecular layers one by one on the support

  12 is done as follows. We open the door

  valve 2 and vacuum is made inside the development tank 1 to about 10'7 - 10-8 Pascal (hereinafter abbreviated as Pa), using a evacuation at high vacuum 3. Then, the GaAs support 12 is heated with the aid of the heating device 10 at a temperature of between 300 and 8000C; we

  opens valve 6 to introduce TMG gas (trimethyl-

  gallium) 8 as gas containing Ga in the reservoir

  0.5 to 10 seconds so that the pressure in the development tank is between 10 '1 and 107 Pa. Then, after the closing of the valve 6 to evacuate the gas in the development tank 1, opens the valve 7 to introduce AsH3 (Arsine) 9 as a gas containing As in the reservoir for 2 to

  seconds to get a pressure of 10-1 ...

  10-7 Pa. Thus, at least one molecular layer is developed.

  The operations described above are repeated in order to successively develop single molecular layers, so as to obtain an epitaxial growth layer of GaAs of desired thickness and with the precision of a single molecular layer. During growth of the crystal, the growth temperature increases and voids and atoms are formed between the networks or the like. Furthermore,

  impurities are taken because of the phenomenon of

  doping or the like, which is not interesting for developing very filled crystals. To avoid this, it is necessary to develop crystals without raising

  temperature. However, according to the process of developing

  known crystals, the temperature of development

  crystals is relatively high and is included in

  300 to 800 C does not allow to obtain a

  monocrystal GaAs whose filling is very thorough.

SUMMARY OF THE INVENTION:

  The present invention aims to

  create a process for developing a semiconductor film

  GaAs single crystal crystal of high quality

  of a single molecular layer, and remedying the

are averse to known solutions.

  Thus, the proposed methods

  Later, the present inventors continue to be developed, whereby TEG and AsH3 are used as gas sources by introducing these gases alternately into the developing tank and under a predetermined pressure for a given period of time to obtain a film. from a very pure GaAs single crystal to a

  low temperature below 300 C.

SUMMARY DESCRIPTION OF THE DRAWINGS:

  The present invention will be described in more detail with the aid of the accompanying drawings, in which: FIG. 1 is a block diagram of a crystal-developing apparatus

  according to an embodiment of the present invention.

  FIG. 2 is a graph showing the relationship between the thickness of the film developed by a crystal manufacturer using the apparatus of the

  Figure 1 and the temperature of the support.

- Figure 3 is a graph of

  the relationship between the thickness of the developed film and the amount of TEG introduced for a temperature

support equal to 290 C.

- Figure 4 is a graph of

  the relationship between the density of the impurities of the film developed with TEG and AsH3 as gas sources as well as the mobility compared to that of a conventional molecular-layer epitaxial film and FIG. 5 is a block diagram of a device crystal development according to

  an earlier invention of the present inventors.

  DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

TIELS:

One embodiment of the invention

will be described below.

  Figure 1 shows the structure of an epitaxial growth apparatus of a molecular layer according to one embodiment of the invention. The same reference numerals as those used in FIG. 5 represent in FIG.

  those of Figure 5 except for the lamp below.

  red used as a source of heat; this lamp comprises a lamp box 31 outside the development tank; the infrared radiation emitted by the casing of the lamp 1 arrives on the support 12 through a quartz glass 32 to heat the support 12 carried

by a receiving means 33.

  In operation of the apparatus, TEG gas (triethylgallium) 6 is introduced as gas containing Ga at a pressure of 10 6 to 10 -2 Pa.

  1 to 20 seconds and evacuate for 1 to 20 seconds

  of. Then, the gas AsH3 (Arsine) 9 is introduced as a gas containing As at a pressure of between 10 -4 and 1 Pa for 1 to 200 seconds, and then evacuated for 1 to 20 seconds. We thus develop a layer

  of GaAs on the support 12. The steps described in

  The above procedures are repeated to successively develop monomolecular layers giving a monocrystal film of GaAs having the desired thickness to

  the accuracy of the monomolecular layer.

  Figure 2 shows the thickness of the film developed in the crystallographic direction

  <111> of the B side of the GaAs film per cycle at a temperature of

  ture between 260 C and 350 C, the parameter being the temperature of the support; in this case, we use

  as TEG and AsH3 feed gas. For a temperature

  With a support ratio of 290 ° C., the GaAs film per cycle had a thickness of 3.2 Å corresponding to a molecular layer. The development temperature of 260 C

  mentioned above is a lower temperature of

  90 C viron at the minimum crystal development temperature of 350 C in the development process

  using the combination of TMG and AsH3 previously

  already proposed by the same inventors.

  FIG. 3 shows the thickness of the developed film of GaAs per cycle for a substrate temperature equal to 2900 ° C., the gas being introduced at a pressure of between 10 -1 and 10 -4 Pa for a duration of 2 to 60 seconds and an evacuation time per cylinder equal to 2-20 seconds, the amount of TEG introduced per cycle constituting a parameter. It appears in FIG. 3 that, if the amount of TEG introduced per cycle increases, the thickness of the developed film reaches

  limit. So for a development done with a quantity

  gas introduced in excess of the value

  saturation, even if the amount of gas varies slightly

  advantageously, the development of a monomolecular layer per cycle is advantageously obtained. So, we can settle

  to the accuracy of the atomic unit, the thickness of the film.

  The epitaxial growth layer thus obtained GaAs was examined by electron beam diffraction and X-ray diffraction; these tests showed

  that the monocrystal film layer was very complete.

Figure 4 shows the relation

  the density of the impurities of a film subjected to a growth

  epitaxial growth of a molecular layer using as

  TEG and AsH3 gas sources as well as mobility by

  parison with a conventional film obtained by epitaxial development of a molecular layer using TMG and AsH3 gases. In FIG. 4, the curve A corresponds to the calculated theoretical value; point B corresponds to a film developed with TEG and AsH3 gases; point C corresponds to a classical epitaxial development of a

molecular layer.

  As shown in this figure, in the prior art, the density of the impurities was high,

  1018 to 1020 cm-3 and mobility was

  less than 100 cm 2 V 1 S-, whereas according to the present invention, the density of the impurities has been improved by 2 to 3 orders of magnitude, that is to say it is from 1015 to 1017 cm 3 and the mobility corresponds to a value

  close to the theoretical value that is to say 360 cm2 V1 S1.

  The film thus developed was prepared under experimental conditions with a TEG pressure of between -3 and 10 -4 Pa, a pressure of AsH3 between -1 and 10-2 Pa, an introduction time of between 2 and 60 seconds and an evacuation time of 2 to 20 seconds. It is clear from Figure 4 that the

  film developed according to the present invention is a mono-

  crystal of high purity, particularly excellent, compared with the epitaxial growth of a layer

classical molecular.

  The crystal impurity density thus obtained was less than 1015 cm-3 and the mobility was greater than 360 cm 2 V-1 S-1. As described above, according to the present invention, the crystals can be developed.

  to one, which makes it easy to satisfy the stoichi-

  metry and have a low support temperature. It is thus possible to manufacture a good quality single crystal with a minimum of network faults on a

support.

  In addition the addition of impurities can be done one by one in the layer and that is why it is possible to achieve an extremely dense density distribution.

  precise for impurities giving excellent characteristics

  functioning and making it possible to manufacture

  transistors, integrated circuits, photo diodes

  emissives or the like having an extreme

fast.

Claims (3)

CLAIMS N E N T I N O I T I N N 5   1) Process of developing a   film of a GaAs single crystal on a carrier by introducing   of a gas containing an elemental compound of the crystal in a development reservoir evacuated with respect to the outside, characterized in that   creates a vacuum inside the reservoir (1) for developing   At a predetermined pressure, TEG Triethylgallium (8) gas is introduced into this development reservoir.   under a predetermined pressure for a predetermined time   completed, and after the evacuation of the TEG gas,   AsH3 gas (Arsine) (9.) in this reservoir of   under a predetermined pressure for a predetermined time and the cycle is repeated to develop at least substantially a molecular layer to form a GaAs single crystal film of desired thickness at the   precision of a molecular layer.   2) Process according to claim 1, characterized in that the heat source is a   outdoor infrared lamp of the development tank   or a heated tungsten wire.   3) Process according to claim 1, characterized in that the average number of layers   molecular weight per gas introduction cycle is lower than to 2. ) Method according to any one   Claims 1 and 2, characterized in that the   the TEG and AsH3 gas introduction pressure is between 1 and 105 Pa, the introduction time is   between 1 and 200 seconds, and the evacuation time   after the introduction of the gas is between 1 and seconds.  ) Method according to any one   Claims 1 to 3, characterized in that the time   substrate temperature is below 300 C.