The method of obtaining epitaxial layer of a semiconductor of the iii - nitride on the substrate alien

 

(57) Abstract:

Use: in the manufacture of semiconductor devices, namely how to obtain a layer of semiconductor of the III-nitride (GaN, AlN, InN) on foreign substrate by vapor-phase epitaxy using ORGANOMETALLIC compounds (MOS). Application: with the development of semiconductor lasers, light emitting diodes, ultraviolet photodetectors, high-temperature diodes, transistors. The inventive when receiving epitaxial layer of a semiconductor of the III-nitride on a foreign substrate by vapor-phase epitaxy from ORGANOMETALLIC compounds, consisting of a stage of formation of the buffer layer and the phase epitaxial growth, using threads MOS and ammonia, exercise pulse mode flow MOS at both stages, and the pulse duration tn(C) at the stage of formation of the buffer layer is determined from the relation tn= rcrn-2/3/v1at the stage of epitaxial growth of te(C) from the relation te=h/v2and duration t(c) intervals between pulses satisfy the relations t>t1t>tewhere n is the number of pulse (1,2,...); rcrcritical radius of the embryo at the height of the heterogeneity of the topography of the surface of the epitaxial layer, v2- the growth rate of the layer at the stage of epitaxial growth, the Technical result of the invention is to improve the quality of the epitaxial layer by reducing the density of defects and dislocations.

The invention relates to methods of manufacturing semiconductor devices, and more specifically to methods of epitaxial growth, namely receiving layer of the semiconductor of the III-nitride (GaN, A1N, InN) on foreign substrate by vapor-phase epitaxy using ORGANOMETALLIC compounds (MOS), and may find application in the construction of semiconductor lasers, light emitting diodes, ultraviolet photodetectors, high-temperature diodes, transistors, etc. In the method of gas-phase epitaxy using MOS growth layer of the III-nitride originates from streams ORGANOMETALLIC (trimethylgal lium (TMG), triethylgallium (TEG), trimethylaluminum (l), and so on) compounds and ammonia (NH3), usually on a sapphire substrate or SiC substrate, Si in two stages (stage of formation of the buffer layer and the stage directly epitaxial growth).

A known method of producing a semiconductor of the III-nitride by the method of two-stage epitaxial growth, such as GaN [1], in which the sapphire podlog is to 1025oWith and grow the core layer. In this way flows of ammonia and trimethylgal lium constant as in the formation of the buffer layer, and in the process of epitaxial base layer. This method allows to obtain epitaxial layers of semiconductors of the III-nitrides, however, its disadvantage is high (109-1010cm-2) the density of defects and dislocations in the epitaxial layer.

The closest technical solution (prototype) is a method for epitaxial GaN layer by the method of vapor-phase epitaxy from MOS in pulsed mode [2]. In this method, the foreign substrate (SiC) is produced by growing a layer in two stages: first, the formation of the GaN buffer layer and a conductive layer of Alof 0.2Ga0,8N at high temperature (1000oC) and at constant flow TEG, TMA1 and NH3then the base layer of GaN at a temperature of 950oC. the Core layer is grown by the rivers of TEG and ammonia, and a stream of ammonia is intermittent (pulsed) nature: within 8 with the flow constant for 5 with a stream of ammonia is missing, then this cycle is repeated several times.

The advantage of this method is that it allows for a more favorable growth conditions in the direction of p is in the direction perpendicular to the surface of the substrate), resulting in higher quality epitaxial layer (as layer 15% higher than in the layers grown by the method similar).

The disadvantage of this method is that the formation of the buffer layer occurs at constant flows of ammonia and TEG, a because the nitrogen atoms have a very low mobility on the substrate (by several orders of magnitude less) than Ga atoms, the origin of the buffer layer is in excess Ga atoms, which creates a large number of defects (due to an excess of Ga) and dislocation. The growth of the base layer by pulsed supply of ammonia allows, apparently, to provide conditions more optimal to move the nitrogen atoms on the surface of the growing layer than at a constant flow of ammonia, which allows us to get more high-quality epitaxial layers in comparison with analogues.

The proposed method solves the problem of improving the quality epitaxial layer of a semiconductor of the III-nitride on a foreign substrate by reducing the density of defects and dislocations.

The task is solved in that in a method of producing epitaxial semiconductor layer of the III-nitride on a foreign substrate OYA and stage of epitaxial growth, using threads ORGANOMETALLIC compound and ammonia, one of which is delivered in a pulsed mode at a stage of epitaxial growth, mentioned pulse mode is performed in the flow ORGANOMETALLIC compound at both stages, and the pulse duration tn(C) at the stage of formation of the buffer layer is determined from the relation:

tn=rcrn-2/3/v1,

at the stage of epitaxial growth te(c) ratio:

te=h/v2,

and duration t(c) intervals between pulses satisfies the relations

t>t1t>te,

where n is the number of pulse (1,2,...);

rSGcritical radius of the embryo at the alien base,

v1- the rate of formation of the layer during the formation of the buffer layer,

h is the initial height of the heterogeneity of the topography of the surface of the epitaxial layer,

v2- the growth rate of the layer at the stage of epitaxial growth,

The decrease of the density of defects and dislocations mismatch is achieved by selecting a qualitatively new conditions as the formation of the buffer layer, and the subsequent epitaxial growth layer. For the formation of a buffer layer on an alien podloga embedded in the surface as atoms III-group and nitrogen atoms. As education centres of the new phase (semiconductor of the III-nitride) on the surface of the alien (e.g., sapphire) substrate is saturation in the well-known methods remains high (at constant flows of ORGANOMETALLIC compounds and ammonia), which leads to the formation of many small nuclei of the new phase, which quickly closed, forming an almost continuous amorphous layer of III-nitride. The formation of larger crystalline regions of the semiconductor of the III-nitride buffer layer takes place when the temperature is raised to 1025-1050oC (annealing the buffer layer). If further growth of the epitaxial layer (as in method-prototype) occurs at a constant flow MOS and pulsating flow of ammonia, since the surface diffusion of nitrogen atoms is substantially less than the surface diffusion of atoms of the III-group and a blast of nitrogen atoms from the surface of the growing layer at high temperatures significant pulsation in the flow of ammonia affects the quality of the growing layer is weak.

In the proposed method, conditions of formation of the buffer layer and the epitaxial growth of the base layer is improved, firstly, due to the pulsed mode under the to at the stage of formation of the buffer layer, and at the stage of epitaxial growth. The selection conditions of the pulsation flow of the MOS allows to reduce the concentration of the atoms of the third group and to reduce the number of defects associated with the excess of these atoms at the inception of the buffer layer. The choice of conditions for the duration of the pulse stream ORGANOMETALLIC compound on a foreign substrate tn=rcrn-2/3/v1due to the fact that the magnitude of this flow, on the one hand, should be sufficient for the nucleation layer, and on the other hand, the flow should decrease pulse according to a certain law ~ n-2/3that could not accumulate an excessive number of atoms of the third group and to increase the probability of formation of new nuclei was small, and the probability of escalation of an already existing embryos was great. As further growth of nuclei is limited by the transfer of atoms across the interfacial boundary, when the fading stream of atoms MOS on the surface of the substrate, if the degree of attenuation of ~ n-2/3for all atoms, the conditions for the formation of new nuclei. This leads to the growth of the Islands and the receive buffer layer over the crystalline centers of the new phase, which upon further annealing creates a better buffer layer. Selection conditions the flow MOS (pulse delivery), moreover, the pulse duration in this phase epitaxial growth is determined by the initial height of the degree of heterogeneity of the surface relief layer (initially, this will be the height of the roughness of the buffer layer) - h. The choice of the time interval t between the pulses t>tnn=1 due to the fact, to ensure complete removal of supersaturation and to provide the movement of nitrogen atoms on the surface of the substrate and embedding them into the centre of a new phase during the absence of flow MOS. The choice of the time interval t>tedue to the fact, to ensure the removal of supersaturation and the movement of nitrogen atoms on the surface of the epitaxial layer during the absence of flow MOS.

The method is as follows. Alien substrate (such as sapphire) prepare the standard method (etching, rinsing, drying) for epitaxy and placed in a reactor for vapor-phase epitaxy from ORGANOMETALLIC compounds. Establish certain of the known literature data [1] threads MOS, ammonia, hydrogen, determine the temperature of formation of the buffer layer and its thickness, the temperature of the epitaxial base layer and determine the velocity v1v2, rSGwhen these conditions. Calculate the duration of a pulse with a constant stream of ammonia and pulse flow MOS with a pulse duration of tn= rSGn-2/3/v1and the interval between pulses t>t1t>te. After the formation of the layer of a specified thickness to stop the flow of MOS, measure the magnitude of the heterogeneity of the surface topography of the buffer layer, heat the buffer layer to a temperature epitaxy and are in contact buffer layer with a pulsed flow MOS with a pulse duration of te=h/v2and the interval between pulses t>tet>t1. After growing the epitaxial layer to produce off flow MOS and the system cooled to room temperature.

Example 1

Were receiving layer of GaN on sapphire (0001) substrate in two stages (first formed a buffer layer of GaN at a temperature of 525oSince then grown epitaxial layer at a temperature of 1050oC) for the installation of epitaxy from ORGANOMETALLIC compounds "Epiquip" in a horizontal reactor with inductive heating. The process was carried out in hydrogen atmosphere, the quality of the reactant gases was used trimethylgal lium and ammonia. The typical growth rate during the formation of the buffer layer was during epitaxial growth and the stream of trimethylgal lium was 3610-3mol/min and 12110-3mol/min, respectively, authorized tasks defined pulse duration tnthe flow of trimethylgal lium during the formation of the buffer layer tn=rcrn-2/3/v1n=1 t1=20c, n= 2 t2=13c, n=3 t3=10c, n=4 t4=8c, n=5 t5=7c, n=6 t6=6c, n=7 t7=5c, n=8 t8= 5c, n=9 t9=5c, n=10 t10=4c, n=11 t11=4c, n=12 t12=3c.

For the first 10 pulses with a total duration of 82 formed a layer about the thickness and it was solid. The rest (given to us layer) raised almost constant pulse t12-t40duration 3s for another 30 pulses. The intervals between pulses were t>t1= 20 c. After the formation of the buffer layer, the temperature was raised to a temperature epitaxial growth 1050oWith and carried out a pulse mode by the flow of trimethylgal lium with a pulse duration of te=h/v2where h is the initial height of the heterogeneity of the topography of the surface of the epitaxial layer defined by laser reflectometry (similar data were obtained by the authors of [3]).

te= 20/1,8 = 11c.

The intervals between pulses were t>tet>t1t>20c.

After growing the epitaxial layer, the process is stopped, the substrate was cooled and used to assess the quality of the resulting layer.

Example 2

Same as in example 1, but the intervals between pulses t<tand t<t.

It turned out that the quality of the layer obtained in this case was worse than the quality of the layer obtained in the prototype.

The quality of the epitaxial layers was estimated by photoluminescence, atomic force microscopy (AFM), x-ray diffraction. It turned out that in the case of example 1:

- the intensity of the edge photoluminescence of GaN layer grown on the proposed method, 2.9 times higher than in the method prototype with the same excitation levels;

- comparison and analysis of the AFM images of the surface area of 200 x 200 nm2showed that the difference between the maximum and minimum elevation 3 times less in the layer grown on the proposed method than in the method prototype, and was the largest

- comparison of the diffraction curves of the layers grown by the proposed method and the method prototype showed that the dislocation density is 10 times lower in the layer is obtained by deposition in the proposed pulse mode.

In the case of example 2, the quality of the resulting layer was lower quality layer grown by the method prototype.

Thus, this method allows the and, than all known methods.

LITERATURE

1. S. C. Jain, M. Willander, J. Narayan, and R. Van Overstraeten. III-nitrides: Growth, characterization, and properties. J. Appl.Phys., v.87, N. 3, pp. 968-1008 (2000).

2. R. S. Qhalid Fareed, J. W. Yang, Jianping Zhang, Vinod Adivarahan, Vhnamra Chaturvedi, and M. AsifKhan. Vertically faceted lateral overgrowth ofGaN on SiC with conducting buffer layers using pulsed metalorganic chemical vapor deposition. Appl. Phys. Lett. v.77, No. 15, pp. 2343-2345 (2000).

3. K. Lorenz, M. Gonsalves, Wbok Kim, and S. Mahajan. Comparative study of GaN and A1N nucleation layers and thir role in growth of GaN on sapphire by MOCVD. Appl. Phys. Lett, v.77, No. 21, pp. 3391-3393 (2000).

The method of obtaining epitaxial layer of a semiconductor of the III-nitride on a foreign substrate by vapor-phase epitaxy from ORGANOMETALLIC compounds, consisting of a stage of formation of the buffer layer and the phase epitaxial growth using threads ORGANOMETALLIC compound and ammonia, one of which is delivered in a pulsed mode at a stage of epitaxial growth, characterized in that the said pulse mode is performed in the flow ORGANOMETALLIC compound at both stages, and the pulse duration tn(C) at the stage of formation of the buffer layer is determined from the relation

tn=rcrn-2/3/v1,

at the stage of epitaxial growth te(C) ratio

te=h/ve,

where n is the number of pulse (1,2,...);

rcrcritical radius of the embryo at the alien base,

v1- the rate of formation of the layer during the formation of the buffer layer,

h is the initial height of the heterogeneity of the topography of the surface of the epitaxial layer,

v2- the growth rate of the layer at the stage of epitaxial growth,

 

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