CN102738267B

CN102738267B - Solar battery with superlattices and manufacturing method thereof

Info

Publication number: CN102738267B
Application number: CN201210203843.2A
Authority: CN
Inventors: 郑新和; 李雪飞; 张东炎; 吴渊渊; 陆书龙; 杨辉
Original assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Current assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Priority date: 2012-06-20
Filing date: 2012-06-20
Publication date: 2015-01-21
Anticipated expiration: 2032-06-20
Also published as: CN102738267A

Abstract

The present invention provides a solar cell with a superlattice structure, comprising a first GaAs layer and an active region, the active region is placed on the exposed surface of the first GaAs layer, and the active region includes a first, a second Two GaNAs/InGaAs superlattice structures, the second GaNAs/InGaAs superlattice structure is arranged on the surface of the first GaNAs/InGaAs superlattice structure, and the first and second GaNAs/InGaAs superlattice structures are The InGaAs layers have different thicknesses. The present invention also provides a method for preparing a solar cell with a superlattice structure as described above. Two GaNAs/InGaAs superlattice structures are grown on the exposed surface of the first GaAs layer to form an active region. The two GaNAs The thickness of the InGaAs layer in the InGaAs/InGaAs superlattice structure is different.

Description

Solar cell with superlattice structure and preparation method thereof

Technical field

The present invention relates to area of solar cell, particularly relate to solar cell with superlattice structure and preparation method thereof.

Background technology

Because solar energy is inexhaustible, be effective replacer of traditional fossil energy, the research of solar cell is more and more deep.In solar cell field, current GaInP/GaAs multijunction cell has been successfully applied to space photovoltaic art, becomes again the outstanding representative of ground high power concentrator application, can form three junction batteries in addition efficiency can be made to be promoted further with Ge because of its peak efficiency.But the band gap of Ge (0.7eV) is not most suitable in three junction batteries.If can prepare the solar cell of 0.8 ~ 1.4eV, and mate with GaAs or Ge substrate lattice, conversion efficiency will significantly promote, and can form four knots and the above Lattice Matching battery obtaining Ultra-High Efficiency of four knots in conjunction with Ge.

Have the low energy gap InAsN of unusual band-gap bowing in recent years, InGaAsN, GaNP and GaNAsP material receives attention.It is found that its band gap of GaAs adding a small amount of nitrogen is not the increase of expection, create reverse effect on the contrary, thus cause band gap to reduce rapidly, it not the blue shift of expection, but red shift, this uncommon behavior causes sizable interest, and it is believed that this is a new viewpoint and there is potential application space in materials physics, these noval chemical compounds are called as rare nitride.Rare nitride has broken away from traditional Group III-V semiconductor, when nitrogen is inserted into the lattice of group-v element, creates profound influence to the performance of material, and allows energy band engineering to further develop.In the GaAs and InP-base III-V of routine, only add a small amount of nitrogen (being less than 5%), result can cause very large band curvature, this results in much interesting microelectronics and photovoltaic applications.Except band curvature, a small amount of nitrogen also causes the change of band structure, only has the nitrogen of 0.5%, and GaP band gap produces from receiving direct change, and has very strong luminescence in 650nm red range.

Now existing researcher prepares the GaInNAs solar cell that band gap is 1eV, as Fig. 1, comprise substrate layer 101, and the resilient coating 102 set gradually on substrate layer 101, back surface field layer 103, a GaAs layer 104, the 2nd GaAs layer 105 and contact layer 106, but this GaInNAs solar cell current density and open circuit voltage still lower, conversion efficiency is not high yet.Adopt the body material of GaInNAs quaternary system, because In, N coexist growth, easy generation strain rises and falls with component, reduce minority carrier life time, mobility is not high yet, the electron-hole pair that absorb photons produces just compound before being collected, limit electric current and export, the lifting of conversion efficiency is limited.Though have the superlattice that are separated by In, N and quantum well to obtain the solar cell of this band gap, owing to being the superlattice of single barrier layer thickness, easily producing misfit dislocation when obtaining enough thick active area, finally affecting the performance of battery.So researcher attempts to find other effective ways and breaks through this technical barrier.

Summary of the invention

Technical problem to be solved by this invention is, provides solar cell with superlattice structure and preparation method thereof.

In order to solve the problem, the invention provides a kind of solar cell with superlattice structure, comprise GaAs layer and an active area, described active area is placed on the exposed surface of a GaAs layer, described active area comprises first, second GaNAs/InGaAs superlattice structure, described 2nd GaNAs/InGaAs superlattice structure is arranged at a GaNAs/InGaAs superlattice structure surface, and the InGaAs layer thickness difference in first, second GaNAs/InGaAs superlattice structure described.

The described solar cell with superlattice structure, comprise GaAs battery and GaAs resilient coating further, described GaAs battery is placed on the exposed surface of GaAs resilient coating, the AlGaAs back surface field layer that described GaAs battery sets gradually, a GaAs layer, active area, the 2nd GaAs layer and AlGaAs Window layer, wherein the conductiving doping type of a GaAs layer is contrary with the conductiving doping type of the 2nd GaAs layer.

The described solar cell with superlattice structure, comprises the substrate layer of Ge or GaAs further, and comprises the GaAs resilient coating, GaAs battery and the GaAs contact layer that arrange on the substrate layer of Ge or GaAs successively.

The periodic regime of first, second GaNAs/InGaAs superlattice structure described is respectively 1 nanometer to 10 nanometer.

In order to solve the problem, present invention also offers a kind of preparation method with the solar cell of superlattice structure, comprising step: 3) in a GaAs layer exposed surface growth active area,

Described step 3) comprises step further:

31) at GaAs layer superficial growth an one GaNAs/InGaAs superlattice structure;

32) at GaNAs/InGaAs superlattice structure superficial growth a 2nd GaNAs/InGaAs superlattice structure;

Wherein, the InGaAs layer thickness in described two kinds of GaNAs/InGaAs superlattice structures is different.

Taking a step forward of described step 3) comprises step:

1) at the exposed surface growth AlGaAs back surface field layer of GaAs resilient coating;

2) at AlGaAs back surface field layer superficial growth the one GaAs layer;

Step is comprised further: 4) at surfaces of active regions growth the 2nd GaAs layer after described step 3);

5) in the 2nd GaAs layer superficial growth AlGaAs Window layer.

Step is comprised: at the substrate layer exposed surface growth GaAs resilient coating of Ge or GaAs before described step 1),

Step is comprised: at AlGaAs Window layer superficial growth GaAs contact layer after described step 5).

The growth pattern that the growth of first, second GaNAs/InGaAs superlattice structure described all adopts In and N space to be separated.

The invention provides solar cell with superlattice structure and preparation method thereof, advantage is:

1. above-mentioned solar cell bandgap range is 0.8 ~ 1.4eV, compared with the GaInNAs battery being 1eV, can form more reasonably band gap and combine, can utilize solar spectrum more fully with GaInP/GaAs and Ge of technology maturation with traditional band gap;

2. above-mentioned solar cell adopts short period superlattice as active area, more convenient modulation band gap size;

3. above-mentioned solar cell active region growth adopts In, N to be separated growing technology, avoids traditional GaInNAs battery active area In, N and to coexist the defects such as the strain that causes;

4. in above-mentioned solar cell active area, the thickness of InGaAs well layer is different, can obtain enough thick active area like this and not produce the defect straining mismatch and cause, thus improving the efficiency of battery.

Accompanying drawing explanation

Fig. 1 is traditional GaInNAs solar cell junction composition;

Fig. 2 is a kind of solar battery structure figure with superlattice structure provided by the invention.

Embodiment

Elaborate below in conjunction with the embodiment of accompanying drawing to the solar cell with superlattice structure provided by the invention and preparation method thereof.

Figure 2 shows that described a kind of solar battery structure figure with superlattice structure.

First embodiment

Of the present inventionly provide a kind of rare nitrogen nitride (Dilute Nitride) superlattice solar cell with superlattice structure.

Described rare nitrogen nitride super lattice solar cell with superlattice structure, the bandgap range of this solar cell is 0.8eV ~ 1.4eV, comprise the substrate layer 201 of Ge or GaAs, and be included in GaAs resilient coating 202, GaAs battery, GaAs contact layer 209 and upper contact electrode 210 that the substrate layer 201 of Ge or GaAs sets gradually, and be included in the lower contact electrode 200 on substrate layer 201 exposed surface of Ge or GaAs.

GaAs battery on GaAs resilient coating 202 successively according to AlGaAs back surface field layer the 203, the one GaAs layer 204 arranged away from substrate layer 201 direction, active area 211, the 2nd GaAs layer 207 and AlGaAs Window layer 208, wherein the conductiving doping type of a GaAs layer 204 is contrary with the conductiving doping type of the 2nd GaAs layer 207.The conductiving doping type of the one GaAs layer 204 is N-type or P type.

As Alternate embodiments, a GaAs layer 204 can be used as the base of GaAs battery, and the 2nd GaAs layer 207 can be used as the emitter region of GaAs battery.

The material of described active area 211 is two kinds of GaNAs/InGaAs superlattice structures, an i.e. GaNAs/InGaAs superlattice structure 205 and the 2nd GaNAs/InGaAs superlattice structure 206, and a GaNAs/InGaAs superlattice structure 205 and the 2nd GaNAs/InGaAs superlattice structure 206 are according to being arranged at GaAs layer 204 surface away from substrate layer 201 direction, wherein the well layer InGaAs of a GaNAs/InGaAs superlattice structure 205 and the 2nd GaNAs/InGaAs superlattice structure 206 has different thickness.

A described GaNAs/InGaAs superlattice structure 205, the 2nd GaNAs/InGaAs superlattice structure 206 are short period superlattice structure, and their periodic regimes are respectively 1 nanometer to 10 nanometer, guarantee like this should ensure source region 211 and not produce mismatch, ensures source region 211 again and obtains required absorption band edge.

Second embodiment

The above-mentioned preparation method with the solar cell of superlattice structure is:

1) utilize metal organic chemical vapor deposition technology (MOCVD) or molecular beam epitaxy technique (MBE) on the substrate layer 201 of Ge or GaAs, grow GaAs resilient coating 202, AlGaAs back surface field layer 203 and a GaAs layer 204 successively;

2) on GaAs layer 204 exposed surface, utilize MOCVD or MBE to grow two kinds of GaNAs/InGaAs short period superlattice active areas 211 with different well layer thickness;

3) on the exposed surface of superlattice active area 211, adopt MOCVD or MBE technology epitaxial growth GaAs emission layer 207, AlGaAs Window layer 208 and GaAs contact layer 209;

4) contact electrode 200 under contact electrode 210 and P type is made in N-type on GaAs contact layer 209 exposed surface and on substrate layer 201 exposed surface of Ge or GaAs respectively.

Next one embodiment of the present of invention are provided.

The invention provides the preparation method of the solar cell with superlattice structure, bandgap range is 0.8eV ~ 1.4eV, and the structure of this solar cell as shown in Figure 2.

To prepare GaNAs/InGaAs short period superlattice solar cell with MBE on the substrate layer of P type Ge, concrete preparation method comprises the following steps:

(1) choose the substrate layer 201 of P type Ge, and substrate is cleaned, the Ge substrate of No clean also can be selected directly to enter next step reaction.Under adopting cooled with liquid nitrogen to coordinate, control lower than 9 × 10 at background pressure ^-10under Torr, substrate layer 201 is placed in the reaction chamber of MBE, and substrate layer 201 is heated to 500 ~ 600 DEG C, to remove substrate layer 201 surface oxide layer, then start the GaAs resilient coating 202 of epitaxial growth non-antiphase domain, use GaAs resilient coating 202 to optimize film quality;

(2) on GaAs resilient coating 202 exposed surface, adopt MBE method growing P-type AlGaAs back surface field layer 203, to reduce the compound of light induced electron, stop the downward contact electrode 200 of light induced electron of a GaAs layer 204 to spread, increase carrier collection;

(3) on AlGaAs back surface field layer 203, adopt MBE method to grow the P type one GaAs layer 204 of carrier concentration lower than back surface field layer carrier concentration;

(4) on the exposed surface of a GaAs layer 204, adopt MBE method growth thickness be the intrinsic of t1/t3 nanometer and have a short-period GaNAs/InGaAs superlattice structure 205 and thickness is the intrinsic of t1/t2 nanometer and has short-period 2nd GaNAs/InGaAs superlattice structure 206.In other words, in one GaNAs/InGaAs superlattice structure 205, the thickness of well layer GaNAs is t1 nanometer, in one GaNAs/InGaAs superlattice structure 205, the thickness of well layer InGaAs is t3 nanometer, in 2nd GaNAs/InGaAs superlattice structure 206, the thickness of well layer GaNAs is t1 nanometer, in 2nd GaNAs/InGaAs superlattice structure 206, the thickness of well layer InGaAs is t2 nanometer, wherein t1, t2, t3 are natural number, and t3 is not equal to t2.

(5) on the exposed surface of active area 211, adopt MBE method to grow N-type GaAs layer as the 2nd GaAs layer 207, then grow the AlGaAs layer 208 of N-type doping content higher than the 2nd GaAs layer 207 as AlGaAs Window layer 208, prevent photohole from upwards spreading.

(6) on the exposed surface of AlGaAs Window layer 208, adopt MBE method to grow the N-type GaAs layer of high-dopant concentration as GaAs contact layer 209, so that battery and metal form good ohmic contact, reduce battery impedance, improve battery performance.

(7) contact electrode 200 under contact electrode 210 and P type is made in N-type on GaAs contact layer 209 exposed surface and on substrate layer 201 exposed surface of Ge or GaAs respectively.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims

1. A solar cell with a superlattice structure, characterized in that it comprises a first GaAs layer and an active region, the active region is placed on the exposed surface of the first GaAs layer, and the active region comprises a first GaAs layer 1. The second GaNAs/InGaAs superlattice structure, the second GaNAs/InGaAs superlattice structure is arranged on the surface of the first GaNAs/InGaAs superlattice structure, and the first and second GaNAs/InGaAs superlattice The thickness of the InGaAs layer in the structure is different, and the first GaNAs/InGaAs superlattice structure and the second GaNAs/InGaAs superlattice structure are short-period superlattice structures.

2. the solar cell with superlattice structure according to claim 1, is characterized in that, further comprises GaAs cell and GaAs buffer layer, described GaAs cell is placed on the exposed surface of GaAs buffer layer, described GaAs cell pack

It includes an AlGaAs back field layer, a first GaAs layer, an active region, a second GaAs layer and an AlGaAs window layer arranged in sequence, wherein the conductive doping type of the first GaAs layer is opposite to that of the second GaAs layer.

3. the solar cell with superlattice structure according to claim 2, is characterized in that, further comprises the substrate layer of Ge or GaAs, and comprises the GaAs buffer layer that is arranged on the substrate layer of Ge or GaAs successively, GaAs cell and GaAs contact layer.

4. The solar cell with a superlattice structure according to claim 1, wherein the period ranges of the first and second GaNAs/InGaAs superlattice structures are respectively 1 nanometer to 10 nanometers.

5. A method for preparing a solar cell with a superlattice structure according to claim 1, characterized in that it comprises the step: 3) growing an active region on the exposed surface of the first GaAs layer, said step 3) further comprising Step: 31) growing a first GaNAs/InGaAs superlattice structure on the surface of the first GaAs layer; 32) growing a second GaNAs/InGaAs superlattice structure on the surface of the first GaNAs/InGaAs superlattice structure; wherein, the two The thickness of the InGaAs layer in the GaNAs/InGaAs superlattice structure is different, and the first GaNAs/InGaAs superlattice structure and the second GaNAs/InGaAs superlattice structure are short-period superlattice structures.

6. The method for preparing a solar cell with a superlattice structure according to claim 5, characterized in that, before the step 3), the step further includes: 1) growing an AlGaAs back field layer on the exposed surface of the GaAs buffer layer; 2) growing the first GaAs layer on the surface of the AlGaAs back field layer; after the step 3), further steps: 4) growing a second GaAs layer on the surface of the active region; 5) growing an AlGaAs window layer on the surface of the second GaAs layer.

7. The method for preparing a solar cell with a superlattice structure according to claim 6, characterized in that, before said step 1), a step is included: growing a GaAs buffer layer on the exposed surface of the substrate layer of Ge or GaAs, said After step 5), a step is included: growing a GaAs contact layer on the surface of the AlGaAs window layer.

8. the preparation method of the solar cell with superlattice structure according to claim 5 is characterized in that, the growth of described first, second GaNAs/InGaAs superlattice structure all adopts the growth of In and N space separation Way.