摘要:

Ion damage of materials due to reactive ion etching and ion‐assisted etching is formulated as a dynamic problem involving the etch rate, damage creation due to ions, diffusion, and ion range effects. The differential equation is solved in the steady‐state assuming an exponentially decreasing damage creation function. The ratioD/aε, whereDis the damage coefficient,athe inherent depth of ion damage, and ε the etch rate is shown to be an important parameter determining the steady‐state damage profile. Results are examined for situations in which the parameter is much less than or much greater than unity, corresponding to range‐ and diffusion‐dominated profiles, respectively. In both situations, steady‐state damage profiles will be quite sensitive to the etch rate of the surface. We suggest some experiments which may elucidate the separate contributions of ion channeling and diffusion to observed damage depth profiles.

ISSN:1071-1023    

DOI:10.1116/1.588358

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A new dry photochemical etching process using HBr gas to selectively remove InGaAs layer over an InAlAs layer has been developed. A 172 nm Excimer lamp was used as the photon source for this experiment. The intensity of the 172 nm light on the surface of the samples was 3 mW/cm2. Etch rates of 62 Å/min and 0.61 Å/min are obtained for InGaAs and InAlAs, respectively, at a chamber pressure of 120 mTorr, sample temperature of 80 °C and HBr flow rate of 10 sccm. These rates translate into a selectivity of over 100 for this material system. Scanning electron microscopy pictures and visual inspection reveal that this process is almost damage free, compared to reactive ion etching. This is due to lack of ion bombardment in the photochemical process. X‐ray photoelectron spectroscopy analysis suggests that the etch selectivity mechanism is due to the formation of nonvolatile  Al2O3on the surface of the InAlAs layer. This etching system should be very useful for fabrication of electrical as well as optical devices based on InGaAs/InAlAs heterojunction.

ISSN:1071-1023    

DOI:10.1116/1.588359

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Quadrupole mass spectrometry (QMS) has been used as aninsitudiagnostic for GaAs etching with a Cl2/Ar plasma generated by an electron cyclotron resonance source. Partial pressure from reactive species and volatile etch products down to 10−10Torr can be detected. AsCl+x(x=1–3) products have been detected from 6×6 mm2GaAs samples. The145AsCl+2signal is generally the strongest. For an increase of microwave power from 50 to 400 W, the GaAs etch rate increased from 151 to 263 nm/min and the145AsCl+2partial pressure increased from 0.6×10−8to 2.8×10−8Torr. The effects of changing source distance, rf power, and pressure were also studied and the changes in etch rate can be correlated to the mass spectrometric intensities of AsCl+x. QMS has been used to monitor the etching of surface oxide on GaAs for different dc biases on the sample. It is found that the oxide etch time is a function of ion energy. For a self‐induced dc bias of −100 V, the145AsCl+2signal remained at 1.4×10−9Torr for the first 15 s of etching. After the oxide was removed the signal increased to 5.5×10−9Torr. O2and N2were added to determine the effects of residual gases in the plasma system. Adding 2.5% O2in the Cl2/Ar discharge caused significant reduction in the etch rate from 171 to 43 nm/min and the145AsCl+2intensity was reduced from 8.0×10−9Torr down to the noise level. For complete substitution of N2for Ar the etch rate only dropped by 1/3 and the partial pressure of the etch products showed a similar decrease. O2was added during an etch to determine the sensitivity of the mass spectrometer to changes in plasma conditions. The decrease in the145AsCl+2signal intensity follows the increase in the16O+2signal intensity with less than 2 s delay.

ISSN:1071-1023    

DOI:10.1116/1.588360

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Numerous device applications of GaAs are hampered by poor electronic properties of GaAs surfaces and interfaces. Room temperature NH3and H2downstream plasma passivation of native oxide contaminated GaAs surfaces is investigated using attenuated‐total‐reflection (ATR) Fourier‐transform‐infrared spectroscopy (FTIR) and photoluminescence (PL). Using ATR FTIR concentrations of –As–O, –As–H, H–OH, and C–H bonds are monitoredinsituand in real time during exposure of the GaAs surface to H (D) atoms from a microwave discharge through NH3(ND3) and H2(D2). Photoluminescence intensity from the GaAs is monitored simultaneously with the FTIR spectra and used as a measure of surface state reduction. At room temperature, H atoms produced from the discharge remove –As–O and C–H contaminants but not Ga2O3. The appearance of As–H bonds and corresponding increase in PL are delayed significantly from plasma initiation, an increase in –O–H concentration, and removal of –As–O bonds. Because the As antisite defects are concentrated at the GaAs–oxide interface, the rates of As–H formation and PL enhancement may be limited by diffusion of H through the oxide and water layer which forms on the surface. We find that the concentration of physisorbed H2O on the GaAs surface increases throughout passivation. There are two sources of water detected on the surface: (i) reduction of As–O bonds and (ii) reaction of H with the quartz reactor walls. Ga2O3grows on the surface via oxidation of GaAs by the physisorbed water. We surmise that higher H concentration in NH3plasmas results in faster water accumulation on the surface and trapping of the As–H species subsurface. In H2plasma, water accumulation on the surface is slower and trapping of As–H is not observed.

ISSN:1071-1023    

DOI:10.1116/1.588361

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

Arrays of all‐optical bistable devices have been fabricated by reactive ion etching (RIE). The vertical Fabry–Pérot structures grown by organometallic vapor‐phase epitaxy include GaAs/Ga0.7Al0.3As multiple quantum wells and AlAs/Ga0.9Al0.1As Bragg reflectors and exhibit optical bistability under moderately focused laser excitation (10–30 μm spot diameter). After RIE, the arrays show a reduced bistability threshold of 70 μW on 4 μm diameter and 5.7 μm high microresonators. This suggests that surface recombination does not play a significant role. This and the absence of degradation of the etched AlAs layers for more than 10 months indicate a self‐passivation of the vertical surfaces during the etching process. Selective plasma etching reveals the presence of a thin cylindrical film clearly visible with a scanning electron microscope. The composition of this film is analyzed by Auger spectroscopy.

ISSN:1071-1023    

DOI:10.1116/1.588362

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

δ‐doped InGaAs/GaAs pseudomorphic double‐quantum‐well high electron mobility transistors grown by low pressure metalorganic chemical vapor deposition are fabricated and demonstrated. The heterostructure with 2 μm gate length and 100 Å channel spacer thickness shows a peak extrinsic transconductance and a maximum saturation current density of 121 mS/mm and 423 mA/mm at 300 K, respectively. Meanwhile, an interesting broad twin‐peak transconductance plateau (∼4 V) is observed.

ISSN:1071-1023    

DOI:10.1116/1.588363

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A novel source switching procedure in gas source molecular‐beam epitaxy achieves abrupt interfaces in lattice‐matched InGaAs/InP. In this procedure, the source supply is interrupted at each interface to reduce excess residual As or P atoms on the InGaAs or InP surfaces. The interruption time is optimized by characterizing the heterointerfaces by Auger electron microscopy and photoluminescence spectroscopy. High‐resolution transmission electron microscopy reveals that each heterointerface of single quantum wells grown by this optimized switching procedure has no transition region. To our knowledge, this is the first successful growth of a perfectly abrupt InGaAs/InP heterointerface.

ISSN:1071-1023    

DOI:10.1116/1.588364

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

UV–ozone substrate preparation and molecular‐beam epitaxial growth conditions of GaAs on (111)B GaAs substrates are reported. Changes in the reflection high‐energy electron diffraction pattern (RHEED) during the first stages of growth reflect the planarization process over an initially rough surface. New evidence of this process is reported, based on the intensity oscillations of the RHEED specular beam, which highlights a rise of the measured growth rate in the first steps of growth during surface flatness recovery.

ISSN:1071-1023    

DOI:10.1116/1.588365

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

A wide range of carbon doping in molecular‐beam‐epitaxy‐grown GaAs and AlGaAs alloys was obtained by means of a new electron‐beam heated solid source. Free hole concentrations from low 1015cm−3to over 1×1020cm−3were reproducibly obtained in GaAs and in direct‐gap AlxGa1−xAs while maintaining good surface morphology. These results extend the doping range in both directions with respect to commercial solid carbon sources. High activation percentage, negligible memory effects and diffusion were demonstrated via secondary ion mass spectrometer and photoluminescence measurements.

ISSN:1071-1023    

DOI:10.1116/1.588366

出版商:American Vacuum Society    

年代:1995

数据来源: AIP

摘要:

We describe a reproducible and precise temperature control system for the molecular beam epitaxial growth of AlGaAs at substrate temperatures in the 700 °C range. Coating of the optical pyrometer window was observed to dramatically affect the pryometer readings making it an unreliable temperature measurement technique. By observing pyrometer interference oscillations during both GaAs and AlGaAs epitaxy, the Ga desorption rate during AlGaAs growth was estimated. The known temperature dependence of the Ga desorption rate allowed the substrate temperature to be calculated, and corrected, when necessary, during the growth. This method allowed the absolute AlGaAs substrate temperature to be controlled within ±3 °C over a six month production cycle.

ISSN:1071-1023    

DOI:10.1116/1.588367

出版商:American Vacuum Society    

年代:1995

数据来源: AIP