I started with a ship full of max-level veterans, and I'm just a complete noob.

The following morning, Wang Shouwu pushed open the door to Laboratory 502. As soon as his gray-blue briefcase was placed on the long table, his gaze immediately locked onto the frequency curve on the blackboard.

"Don't look at the tallest one among these twenty-seven pipes yet."

He walked straight to the blackboard, his pen tracing the distribution diagram from left to right, the tip moving back and forth between 120 MHz and 150 MHz, finally landing on the curve that almost converged into a band.

"Look at this section, the distribution is too concentrated. If it were just a process fluctuation, the curves wouldn't converge so evenly."

Jiang Ming took three photomicrographs out of the file bag and arranged them below the blackboard according to the tube numbers. Fang Xudong had drawn the two junction boundaries on the photos with a red pencil, and the widths of the base regions were marked as 0.6, 0.65 and 0.7 micrometers, respectively.

"The design value is 0.5 micrometers, but the actual base area is 20% to 40% wider, and this factor is the first thing that slows down the transit time."

Wang Shouwu bent down to look at the photo. His gold-rimmed glasses slid down to the middle of his nose. He raised his hand to adjust them, and his gaze followed the boundary of the junction region to the edge of the wafer. Then he picked up the first device card and turned to the page on diffusion records.

Boron diffusion at 620 degrees Celsius for two hours, phosphorus diffusion at 560 degrees Celsius for three hours, estimated silicon dioxide deposition film thickness of 0.2 micrometers, nitrogen flow rate and propulsion position were all filled in by Fang Xudong column by column, and even the changes in furnace tube pressure during the cooling process were recorded.

"The second batch has undergone surface treatment modification, and the frequency can be raised to 160 to 180 MHz, while the base region width is only partially reduced."

Wang Shouwu touched the line of data with the end of his pen, then looked back at the blackboard.

"The improvements brought about by the surface treatment are as you predicted?"

"We also need to integrate photoconductivity spectrum."

Jiang Ming took out a stack of copied curves from the canvas bag. The top one had Xie Xide's sample number written on it. Below the curves were three processing states: pickling, low vacuum annealing, and silicon oxide deposition. Next to it was an estimated value of the surface state density.

Fang Xudong took the curve, spread it out on the long table next to the blackboard, and divided the leakage data of the twenty-seven tubes into three groups according to the chip number. Jiang Ming then used chalk to draw the surface composite path on the blackboard.

"The high leakage current region at the interface of the first batch of tubes coincides with the central defect peak in Comrade Xie's photoconductivity spectrum. The peak value of the second batch decreased after acid washing and vacuum annealing, and was further reduced after the deposition of the protective film."

Wang Shouwu picked up a curve and looked at it for a moment in the light by the window.

"The recombination rate caused by surface states is about one-third of the recombination rate in vivo."

"Based on the low birth rate life expectancy, the extra transit time increases by about 10% to 15%, and the frequency changes of the first and second batches can also be matched."

Jiang Ming wrote the two sets of data on the blackboard. The first set was marked with the contribution of the base region width, and the second set was marked with the contribution of the surface composite. When the two percentages were added together, there was still a gap left in the total deviation.

Wang Shouwu stared at the blank space and tapped his fingers lightly on the table a few times.

"Phosphorus concentration gradient within the base region".

Jiang Ming turned to look at him.

"You think the pace of development is too slow?"

"Low-temperature long-term diffusion makes it easier to achieve a deep junction, but the gradient may not be steep enough. The drift electric field in the base region is weak, and the charge carriers can only pass through by diffusion, which will further reduce their speed."

Wang Shouwu took the chalk and added a steeper line next to the diffusion curve drawn by Jiang Ming. Then he drew the actual concentration distribution from the top of the curve toward the base region, and the difference between the two fronts gradually became apparent.

Looking at the two lines, Jiang Ming replayed the temperature records in the diffusion furnace in his mind. The long-term heat preservation at around 600 degrees Celsius had indeed resulted in sufficient sintering depth. However, the germanium oxide film in the furnace tube repeatedly cracked in the higher temperature zone. The longer the window edge was subjected to the heat process, the higher the leakage current and lateral diffusion would be.

"Increasing the temperature can improve the concentration gradient, and the masking membrane will be the first to give way."

"Then change the camouflage material."

"Materials, equipment, and time all need to be rearranged."

After Jiang Ming finished speaking, he put the chalk back in the trough. Fang Xudong handed Wang Shouwu two batches of diffusion cross-sectional diagrams at 580 degrees and 620 degrees. The diagrams showed that the film layer still curled up after the temperature dropped, but the boundary narrowed and the lateral diffusion also decreased.

Wang Shouwu looked through the two diagrams. The focus in his eyes, which was to break down each process step, was still there, but he felt an added layer of pressure. He had realized that this batch of tubes was not stuck on a single fault. Several small problems were piled up together, which forced the frequency into the same narrow band.

"I prefer to do another round, with 69% germanium material, changing the surface treatment to acid pickling followed by direct vacuuming, raising the diffusion temperature, shortening the time, and trying to reduce the base region width back to 0.5 micrometers."

"Can it reach 250 megahertz?"

"If conditions are favorable, we can also strive for 300 megahertz."

Wang Shouwu spoke quickly, his words carrying the stubbornness familiar to materials researchers. He was willing to admit that there were gaps in the process, but he was unwilling to push the conclusion to the boundaries of materials.

"We should start with mid-frequency applications, and explore alternative approaches for 24 GHz preamps. Cavity oscillators and parametric amplifiers can also be included in the preliminary research."

As Jiang Ming listened to his instructions, his gaze fell on a piece of paper on the corner of the table that read "Frequency is destiny." The edges of the paper were slightly curled up by the lamplight, and next to it were three photomicrographs of dissected tubes.

Wang Shouwu's push for germanium triodes to 300 MHz is already a pragmatic judgment. If he were to say at this point that the high-frequency ceiling for germanium is around 500 MHz, the other party would only see the source of the conclusion, and the materials, crystal orientation, and surface technology of the previous months would be misunderstood as a failed approach.

Jiang Ming opened the kraft paper notebook and wrote down three lines of data on a blank page.

Germanium has a bandgap of 0.67 electron volts.

Silicon, 1.12 electron volts.

Gallium arsenide, 1.42 electron volts.

He then drew the bandgap below the three lines of data, adding three arrows representing the intrinsic carrier concentration, breakdown voltage, and surface state influence. When the pen tip landed on the germanium line, a shallow mark was pressed into the paper.

"I agree with all the improvements you suggested."

Jiang Ming closed the notebook and pushed it back to his side.

"At the same time, we need to start preparing for the second path."

Wang Shouwu raised his head.

"What is the second path?"

"Let's run the device data again for another round of testing before having a full discussion."

Jiang Ming slowly put the three dissected photos back into the file bag, his movements slow and his tone measured.

"We still need one more round of process data. We need to thoroughly examine the base region, surface states, and doping gradients before our conclusions can stand up to scrutiny."

Wang Shouwu looked at him and realized that there was a hidden meaning in his words, but he couldn't tell what kind of device or material was behind it. He turned to a blank page in his thin notebook, wrote down the problem of the cutoff frequency of the germanium triode, and listed the five sources that Jiang Ming had mentioned one by one.

Base region width.

Surface composite.

Doping gradient.

Material purity.

Test link.

At the end of the last line, he drew a question mark, and the tip of his pen lingered next to the question mark for longer than in any of the previous lines.

When Fang Xudong was organizing the curves, he saw the question mark. He twirled the pencil in his hand on the paper. He wanted to ask Wang Shouwu which item he suspected, but he swallowed the words back.

Wang Shouwu closed the notebook.

"When the next batch of samples comes out, send me the original records first."

"Can."

"Send the surface state data as well."

"The original spectral lines on Comrade Xie's side should be based on her number."

Wang Shouwu nodded, picked up the gray-blue briefcase on the table, and glanced back at the blackboard before leaving. The twenty-seven frequency points were densely arranged, like a group of nails being pulled by the same rope. Although the highest point was higher than the other data, it still failed to exceed 200 megahertz.

As the footsteps outside faded into the distance, Fang Xudong tucked the last curve diagram into the file before asking, "Engineer Jiang, do you already know the second route?"

Jiang Ming folded the page with the data written on it into the inner layer of the notebook.

"Knowing a direction."

"Teacher Wang is still pushing the technology forward."

"The process should be pushed forward, and the data should continue to be collected."

After he finished speaking, he raised his hand and turned off the incandescent light next to the blackboard. The frequency curve on the blackboard receded into the darkness, leaving only the dense chalk marks around 130 MHz in sight.

Back in his dormitory at night, Jiang Ming placed his old hardcover memo on the table, turned to a blank page, wrote down the words "pioneer of device physics," and then put the pen aside.

The questions we need to ask this time go beyond a single process improvement. The bandgap of germanium, carrier transport, and high-frequency junction capacitance must all be considered in the same context.

He closed his eyes, and the outline of the old laboratory of the Tongtian Record emerged from the darkness. The stone wall in the distance, the long table piled with glassware, and a dim experimental lamp gradually became clear. A blackboard without any writing on it hung on the wall.

Jiang Ming raised his hand and pushed open the door.