Dietmar Schmitz

Replacement of hydrides by TBAs and TBP for the growth of various III–V materials in production scale MOVPE reactors

Besides the standard group V precursors AsH 3 and PH 3 , so-called alternative precursors like TBAs and TBP (tertiary-butyl-arsine and tertiary-butyl-phosphine) are more and more important in todays MOVPE processes. A lot of publications have demonstrated that these precursors can be successfully used for the growth of different III-V materials. In this study we want to demonstrate that TBAs and TBP can be used as the group V precursor in a complete family of production scale reactors. It is shown that these precursors can be used for the growth of InP-based as well as for GaAs-based materials. The reactors that have been employed are medium scale reactors (AIX 200/4; 1 x 2 inch, 3 or 4 inch or 3 x 2 inch capability) and large scale Planetary Reactors®, in particular the AIX 2400 system (15 X 2 inch or 5 X 4 inch). Materials that have been grown are (Al)GaInP on GaAs and GaInAsP on InP. The lower cracking energy of these precursors compared to PH 3 and AsH 3 allows one to use lower growth temperatures and lower V/III ratios, particularly in combination with the high cracking efficiencies of the used reactors. For the growth of GaInAsP on InP, the consumption of TBP and TBAs is up to 8 times lower than using PH 3 and AsH 3 . GaInP on GaAs could be grown with a V/III ratio as low as 25 in a Planetary Reactor®. Good crystalline quality is demonstrated by DCXD (e.g. for GaInP: FWHM = 35 arcsec, substrate 32 arcsec). PL intensity and growth rate are not affected by using the alternative precursors. The compositional uniformity is similar to layers grown with arsine and phosphine (e.g. 1.5 nm uniformity for GaInAsP (λ = 1.5 μm) on 2 inch; approximately 1 nm uniformity for GaInP) [1,2]. The purity of the grown layers depends mainly on the quality of the TBP and TBAs. Using high purity TBP, InP revealed background carrier concentration in the mid 10 14 cm -3 regime. Our investigation shows that TBP and TBAs can replace phosphine and arsine in state of the art MOVPE reactors. Both for single and multi-wafer production MOVPE reactors these compounds can be used successfully for the growth of the entire material spectrum in the Al-Ga-In-As-P system.

A novel reactor concept for multiwafer growth of III–V semiconductors

Abstract Since the invention of the Planetary Reactors® a reliable tool for mass production of various III–V compounds has existed. These reactors have proven to grow extremely uniform films together with a highly efficient utilization of the precursors. Now a new generation of Planetary Reactors® is introduced: the so-called G3 systems. Their main features are: an inductive heating system with extremely low thermal mass for precise and fast heating, high flexibility in the reactor size (15×2″, 35×2″ to 9×4″ wafers per load so far, further enlargement possible) and the option to use a fully automated cassette-to-cassette wafer loading system. The benefits of this new design are very short cycle times, extreme run-to-run stability and even further reduced cost of ownership. The performance of this reactor will be discussed in conjunction with the well established AIX 2400 reactor with a set up of 15×2″ or 5×4″ wafer. Uniformity of thickness, luminescence intensity and composition of the most important III–V compounds such as GaInP, GaInAsP and AlGaInP are shown.

Growth of extremely uniform III–V compound semiconductor layers by LP-MOVPE by application of the gas foil technique for substrate rotation

Abstract In this study we will report on the first application of gas foil rotation in low pressure systems for growth of InP and GaAs based materials. Commercial reactors could be retrofitted with compatible designed susceptors allowing single rotation and planetary motion. The growth of GaAs/AlGaAs structures has been studied in the horizontal large scale low pressure reactor (5×2 inch wafer) using planetary motion of the wafers. Wafer-to-wafer uniformity of AlGaAs layer thickness of about 1% and compositional uniformity better than 0.4% have been achieved. InP and GaInAsP (λ=1.3 μm) have been grown under the same conditions yielding optimum material on the static susceptor. The thickness variation of these materials was less than 1.5%. The same numbers were found for dopant incorporation (SiH 4 ) at an average concentration of 10 16 cm -3 . Variation of lattice mismatch of GaInAs layers was less than 2×10 -4 over the wafer area. Photoluminescence wavelenght variation of quaternary layers of less than 3 nm could be obtained.

GaInP multiwafer growth by LP-MOVPE for HBTs, lasers, LEDs or solar cells

Abstract This paper reports a new study of LP-MOVPE process for multiwafer applications in ternary GaInP alloys, rivalling substitution or adding to AlGaAs in a variety of applications, such as HBTs, lasers, LEDs or solar cells. Rising demand for these consumer applications has been driving the development of GaInP multiwafer reactors with high volume throughput. The low pressure planetary reactor has been used in this investigation. It has the capability to grow on multiple wafers at the same time for qualification, characterization or device processing. This eliminates uncertainties from single wafer reactors and allows absolute identical growth conditions for different substrates in the same run for studies of substrate effects.

Submicron-gate InP power MISFET's with improved output power density at 18 and 20 GHz

The microwave characteristics at 18 and 20 GHz of submicron-gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFETs) for high output power density applications are presented. InP power MISFETs were fabricated with 0.7 mu m gate lengths, 0.2 mm gate widths, and drain-source spacings of 2, 3 and 5 mu m. The output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacings of 3 mu m. At 18 GHz output power densities of 1.59 W/mm with a gain of 3.47 dB and a power-added efficiency of 20.0% were obtained for a drain-source spacing of 3 mu m. At 20 GHz output power densities of 1.20 W/mm with a gain of 3.17 dB and a power-added efficiency of 13.6% were obtained for a drain-source spacing of 3 mu m. >

InGaAs field-effect transistors with submicron gates for K-band applications

Depletion mode InGaAs microwave power MISFETs with 0.7 mu m gate lengths and 0.2 mm gate widths have been fabricated using an epitaxial process. The devices employed a plasma deposited silicon dioxide gate insulator. The RF power performance at 18 GHz, 20 GHz, and 23 GHz is presented. An output power density of 1.04 W/mm with a corresponding power gain and power-added efficiency of 3.7 dB and 40%, respectively, was obtained at 18 GHz. This is the highest output power density obtained for an InGaAs based transistor on InP at K-band. Record output power densities for an InGaAs MISFET were also demonstrated to the stable within 3% over 17 hours of continuous operation at 18 GHz. >

Investigation of GaInN films and development of double-hetero (DH) structures for blue and green light emitters

Abstract GaInN single layers were investigated in order to optimise their photoluminescence properties and to find dependencies on the main growth parameters such as growth temperature, In/(In+Ga) gas phase ratio and total pressure. Several approaches for capping GaInN/GaN with another GaN layer in order to develop high quality double-hetero (DH) structures were presented. Using an optimised interfacing technique we obtain device quality DH structures with state of the art composition uniformity across a 2″ wafer. Further investigation of these DH structures results in high quality single quantum well (SQW) and multi quantum well (MQW) structures.

High Quality Al-Ga-In-N Heterostructures Fabricated by MOVPE Growth in Multiwafer Reactors

We present results on the growth of Al-Ga-In-N films in multiwafer reactors with 7×2″ wafer capacity. The design of these reactors allows the combination of high efficiency (TMGa efficiency for GaN around 30%) and excellent uniformity. Results on the growth of all materials from the Al-Ga-In-Nitride family are presented in detail. GaN is grown with an excellent optical quality and very good thickness uniformity below 2% across 2″ wafers. The material quality is shown by electron mobility of more than 500 cm 2 /Vs at an intentional Si-doping of approximately 1×10 17 cm −3 . Controlled acceptor doping with Mg yields carrier concentrations between 5×10 16 and 10 18 cm −3 . The layer thickness uniformity of the films are better than 2% over a 2″ wafer area. GaInN is grown with PL emission wavelengths in the visible blue region showing a uniformity better than 1.5 nm standard deviation. The film thickness uniformity represents the same figures as obtained for the binary. The compositional uniformity of AlGaN is in the sub 1% range corresponding to a wavelength variation below 1 nm. The fabrication of heterostructures from these binary and ternary materials is described as well as results from the characterization of these structures. The results show that reliable and efficient production of Al-Ga-In-Nitride based optoelectronic devices can be performed in multiwafer reactors.