혼합소스 HVPE 방법을 이용한 화합물 반도체 결정성장 및 소자 연구

Abstract

Compound semiconductor is largely used as a material with which many kinds of optical devices, electronic devices or solar cell, widely employed in everyday life, are made, In particular, nitride semiconductor with wide direct bandgap is largely applied as optoelectronic which emitting and detecting the light of blue&#8208

source HVT method. This suggests that HVT method can be also one method among the forming methods of nano structures with CIGS or CIS structures, and it is expected to be economic and useful method for the CIGS nano structure photovoltaic production.

source HVT method, nanoplatelet or nanorod types were shaped at 900 ℃ of temperature of growth area, and nanotorpedo was shaped at 950 ℃ of temperature of it. Cu, In and Se were detected as the nano structures formed from EDS. For the Ga source, nano structures were not detected over a certain temperature level of growth area. This suggests that the reactivity of Ga metal is influenced by the temperature of growth area. When the temperature of growth area exceeded 900 ℃, CIS nano structure without Ga was formed from GIGS one. This is determined to be the application case of SLS mechanism used in synthesizing CuInS2.

Based on this result, the nano structures with CIGS or CIS structures were formed by using the mixed&#8208

evaporate method, previous GIGS thin film manufacturing one, but by using HVT, a newer method. For the growth of GIGS, four elements, Cu, In, Ga and Se are put into one graphite boat with mass ratio of 3: 3: 1: 4, and synthesized at 1090 ℃ for about one and a half hours. Then, it was grown by HVT method after the production of a power form of GIG pellet with a mortar in order to enhance the uniformity of materials composition. Therefore, the GIGS structure of hexagonal plate was formed in the shape of butterfly, and Cu, In, Ga, and Se were detected from the measurement of EDS.

By fixing the temperature of source area at 750 ℃ and changing that of growth area from 850 to 900 to 950 ℃, the modifications of GIGS nano structure were observed, according to the temperature change of growth area. When the temperature of growth area was 850 ℃, the nano structures were formed in the shapes of nanohair, nanospoon, and nanorod. Each shapes of nano structure seemed to be formed according to the compositions of Cu, In, Ga and Se. As a result of EDS, Cu, In, Ga and Se were measured in two types except for nanorod grown into the shape of spoon. In general, the nano structures of GIGS formed on substrates were not grown in a constant direction. This is determined not to be influenced by the atom arrangement of substrates.

When the GIGS nano structures were formed by using the mixed&#8208

source method is well utilized, LED research will be economically supported through the method to produce the UV LED.

CIGS thin film and nano structure were grown not by the co&#8208

UV LED with multilayer structure was produced by using the HVPE method.

If the mixed&#8208

UV LED which has stronger traits: better operation voltage and reverse voltage property. The SAG&#8208

V and aging, it is expected to produce the SAG&#8208

source HVPE method.

Although some flaws such as nanopipes occurred around AlGaN active layer grown from TEM result, the dislocation from substrate was not observed. This result shows that the SAG method serves to reduce the dislocation between substrates and growth material. If the conditions of metal and thermal processes are optimized from the measurement of I&#8208

UV LED can be successfully grown with the mixed&#8208

source method was proved to be an another method to solve the problems above, which demonstrates that SAG&#8208

UV LED grown with the mixed&#8208

source HVPE method. In general, if the composition of Al in UV LED exceeds over 30%, the problems between Al and oxygen and difficulties related to the use of AlN substrate may be occurred. However, SAG&#8208

wavelength of EL, As the atomic fractions increase, the main wavelengths seemed to be move into short wavelength area. This result suggests that the modification of wavelength can be controlled depending on Al compositions, with the mixed&#8208

sliding boat.

The result of EL measurement, after metal process and thermal treatment, suggests that when the atomic fractions of Al of active layer are 0.05, 0.12, 0.26, each mean wavelengths of sample was 330, 300, 280 nm, respectively. Each compositions of Al was calculated as 25, 38, 45% by using Vegard’s law on the basis of the mean&#8208

cap layer, which were in turn grown by using the multi&#8208

doped GaN as p&#8208

clad layer and Mg&#8208

doped AlGaN as p&#8208

clad layer, AlGaN according to the atomic fraction of Al(0.05, 0.12, 0.26) as active layer, Mg&#8208

doped AlGaN as n&#8208

doped GaN, Te&#8208

UV DH structure grown with HVPE consists of Te&#8208

UV LED used the selective area growth method(SAG) which has the advantage to reduce the dislocation from the substrate. The SAG&#8208

template was used and the structure of SAG&#8208

source HVPE method. Sapphire substrate with GaN&#8208

UV LED was febricated by using the mixed&#8208

type GaN crystal.

Based on the basic experiment above, SAG&#8208

type but also p&#8208

source HVPE method. And this method can be very useful in getting not only n&#8208

doped GaN by the mixed&#8208

4.2×1017 /cm3, for 0.023. The more atomic fraction increased, the more carrier concentration increased. These results suggest the possibility of the growth of Mg&#8208

2.6×1017 /cm3, for 0.011

type dopant for the doping of GaN. For the source, three samples were prepared by applying 0.04, 0.08, 0.16 g of Mg into 20 g of Ga, and each atomic fractions of Mg were 0.005, 0.011, 0.023. The results of Hall measurement are as follows: the carrier concentration was 1.4×1017 /cm3, for 0.005 of atomic fraction of Mg

doped GaN layer was grown by using the Mg as a p&#8208

doped GaN layer was also increased. The carrier concentration is usually known to be linearly increased according to the amounts of dopant.

Mg&#8208

type dopant. The amounts of Te was modified from 0.14 to 1.6 g, with 20 g of Ga, and the atomic fraction was calculated from 0.0038 to 0.041. The carrier concentration ranged from 1.8×1017 /cm3 to 1.0×1018 /cm3. As the atomic fraction of Te was increased, the carrier concentration of Te&#8208

source HVPE method.

For the doping of GaN layer, Te was used as a n&#8208

source. Based on the findings above, the potential growth of the AlGaN layer is shown, with the mixed&#8208

source of Ga and Al, because of the difference of distribution coefficient of Al in liquid source boat of Ga and Al of mixed&#8208

source of Ga and Al or the decrease of Al distribution on solid AlGaN layer due to the oversaturation of liquid mixed&#8208

distribution of liquid mixed&#8208

ω scan measurement shows AlGaN(0002) peak. Based on the XRD peak, the composition rations of Al were approximately calculated as 30, 42, and 55%. It is determined that the reasons why Al composition is not linearly increased in spite of the increase of Al atomic fraction are the increase of Al distribution on solid AlGaN layer due to the over&#8208

source HVPE method was grown into three types of 0.05, 0.12, 0.26 according to atomic fraction. From the SEM measurements, it was shown that the more Al atomic fraction is increased, the more island or hillock on the surface are tended to be increased, and the result of XRD 2θ&#8208

doped GaN layer are examined by the same method. Based on the basic experiment above, the traits of ultra violet LED devices, produced by forming the DH(double hetero) structure of AlGaN active layer, were evaluated. And the CIGS(CuInGaSe2) thin film, a kind of compound semiconductor, was fostered by using the HVT(hydride vapor transport) method which was a new method suggested in this study.

On the other hand, it is known that AlGaN layer is difficult to be grown evenly by using HVPE method. With this method, hillock or island forms of flaws are likely to be occurred from the concentration of Al because the response coefficients of Al with ammonia are higher than those of it with Ga. Hence, the thick film AlGaN crystal growth of even surface is not easy and there are also many obstacles to the crystal growth due to the combination with oxygen or nitrogen. As the growth of thick AlGaN layer with composition of even Al is not easy, it has been known that a lot of researches and new technologies would be needed in the future.

In this study, the AlGaN layer grown by using the mixed&#8208

doped GaN crystal are investigated by this method. And those Mg&#8208

state by adjusting atomic fraction in aqueous phase of solution, and the growth and property of matter of Te&#8208

source HVPE method that is a new one to control the composition in solid&#8208

efficient solar cell material to dramatically improve the economy of photovoltaic generation by replacing the expensive crystalline silicon solar cell currently used.

The HVPE method with which nitride semiconductor can be grown at the rate from dozens to hundreds μm, faster than with MOCVD or MBE method, is largely used for the GaN substrate production of thick film. Because of this trait, multilayer structure such as LED of thin structure is difficult to be grown with the HVPE method.

In this study, we suggests the mixed&#8208

optic stability of it is very excellent for the long run. Hence, it is emerged as an inexpensive, high&#8208

1 which is higher figure than that of any other semiconductors, so high efficient solar cell can be produced even with 1~2 μm thin film, and the electro&#8208

green UV range, due to its advantageous traits: high thermal conductivity, strength and chemical stability. Although light emitting diode(LED) is more highly commercialized and developed than any other devices, it has some tasks to solve the problems, such as defects, dislocation density, electrical conductivity and crystal quality.

The CIGS, another kind of compound semiconductor, is the Ⅰ­Ⅲ­Ⅵ2 chalcopyrite compound semiconductor with direct bandgap and optical absorption coefficient, 1×105 cm&#8208