In Metal Organic Molecular Beam Epitaxy (MOMBE) the selective area epitaxy (SAE) of double heterostructures (DH) lasers was investigated by using as group V starting materials tertiarybutylarsine/tertiarybutylphosphine (TBAs/TBP), ditertiarybutylarsine/ditertiarybutylphosphine (DTBAs/DTBP) and AsH3/PH3. In Zn-doped InP layers a reduced doping efficiency was found for the process using organic group V precursors whose dissociation chemistry can explain this observation. The growth of GaInAsP close to InP (Q 1.05) using TBAs/TBP reveals that there is a distinct change in the elemental incorporation compared to the hydride process. Thus individual tuning of the growth parameters for different precursors is required. The selectively grown laser ridge structures compare well with large-area grown reference structures. The shape of the ridge is perfectly rectangular when Be-doped p-type cladding layers are used, whereas Zn doping yields a slight multifacet formation at the ridge sidewalls.

The growth of high purity InP layers using trimethylindium (TMIn) and different commercial tertiarybutylphosphine (TBP) batches as well as ditertiarybutylphosphine (DTBP) as a new phosphorous precursor was studied in a production type metalorganic molecular beam epitaxy (MOMBE) growth chamber. The cracking behaviour of TBP was investigated by mass spectrometry. Increasing the beam equivalent pressure from 10(-6) Torr to growth relevant pressures in the 10(-5) Torr range, a transition of the pyrolysis regime was observed, accompanied with a reduced H-2 + P-2 production and a strong formation of the hydride PH3 and dihydride P2H4. This behaviour depends on the conditions on the cracker surface and indicates that the decomposition of TBP occurs by a radical formation process. At 77 K the deposited InP layers exhibited Hall mobilities better than 100000 cm(2)/V s for the use of three TBP batches from two different suppliers with a best value of 167000 cm(2)/V s at n = 1.4 x 10(14) cm(-3). The linewidth of the donor bound exciton in the 1.8 K photoluminescence spectrum of the sample with the highest electron mobility was about 0.09 meV. The first use of DTBP in MOMBE for the growth of high purity InP was also encouraging. The best value of the Hall mobility at 77 K was 77300 cm(2)/V s with n = 5.1 x 10(14) cm(-3). (C) 1998 Elsevier Science B.V. All rights reserved.

The cracking behaviour of PH3, TBP and DitBuPH, AsH3 and TBAs was studied by mass spectrometry in a production-type MOMBE growth chamber. The measurements were performed varying the cracking temperature of the injector cells and the total material flux. The pyrolysis of the hydrides PH 3 AsH 3 essentially leads to the production of hydrogen and the dimers P 2 As 2 . The decomposition of these source materials reaches about 90% at beam pressures in the range of 10−7 Torr. Under identical conditions TBP, TBAs and DitBuPH are cracked better than 97%. However, the pyrolysis of the alkyl-compounds is accompanied by the formation of isobutene and hydrides. Consequently the decomposition of this PH3 and AsH3 produced during cracking is limiting the growth relevant cracking efficiency to the values obtained for the hydrides. The additional occurrence of dihydrides at beam pressures in the range of 10−5 Torr suggests an initial decomposition process of the source materials via a radical formation mechanism. With respect to the stability of the compounds a self-dissociation of TBAs in the bubbler under the production of isobutane C4H10 and AsH3 was detected.

In a comparative study we have chosen TBAs and TBP as well as AsH3 and PH3 for the growth of InPGaInAs(P) heterostructures for laser applications in a production metalorganic molecular beam epitaxy (MOMBE) system. The n-type doping was performed with Si from an effusion cell, whereas for the p-type doping Be and DEZn were utilized. InP layers using TBP under optimized cracking conditions exhibit excellent surface morphology with good electrical properties in the low 1015 cm−3 range of carrier concentrations. The MOMBE growth mechanism is not disturbed by the hydride replacement compound. This allows for a convenient replacement without losing calibration data from the hydride process. Broad-area DH laserstructures with GaInAsP (λ = 1.55 μm) active regions were grown with AsH3PH3 and TBAsTBP. Comparable threshold current densities in the range of 1.6-2.3 kA/cm2 are achieved for the lasers, grown with both sets of precursors combined with DEZn source doping. These results are in good agreement with the standard set by the hydride MOVPE process.