I have done solarization on lawns a few times to start wildflower meadows. It works great for that. They way I did it does not loosen the soil. I mowed the grass as low as I could to weaken the grass, and then covered with clear plastic and covered the edges with scrap lumber, rocks, bricks, etc. It is important to do it during the warmest, sunniest time of year. In Pennsylvania, that is July & August. As soon as you pull up the plastic, spread your wildflower seed. The grass is dead, and most of the weed seed does not germinate.
I have tried a few types of plastic, and even the cheapest stuff you can find will work, but timing is really important. Your really want to solarize during the 2-3 warmest/sunniest months of the year, and then pull the plastic and sow seed right away before new weed seed blows in. The cheapest/thinnest plastic I tried did last the 3-ish months before shredding. "Sunny" in Pennsylvania in July/August is rather hazy, so a drier/hotter location might kill the plastic faster.
Regarding nuking the soil... Call me an optimist, but I hope that some of the creepy crawlies escape to soil that is less warm. The ones that don't end up as fertilizer. If figure it does not take long for for the life in the surrounding soil to start moving back into the solarized areas as soon as the temperature cools off. The good thing with this technique is that it does not destroy the structure of the soil, so I hope the soil can recover more quickly. In any event, the soil is not too "dead" for wildflowers to thrive.
I solarized my
lawn to reduce the amount of lawn work and to bring in beneficial insects, birds, etc. The flowers were a nice benefit too. The first time I did this was in a very suburban neighborhood. Every last neighbor thought I was crazy during the process, but every single one then admitted how cool it was to have months of flowers instead of a sea of green grass. My yard became the neighborhood public garden. I am really happy with the results and love my wildflower meadows, so I will likely continue to do this until most of my mowable lawn is replaced.
Solarization for a wildflower meadow works well, because wildflowers do not need rich soil. They actually prefer the soil that the grass has destroyed. My hope is that the meadow is helping build the soil with very little input, and then all the beneficial critters the meadow brings in will help my other
permaculture efforts. The wife also likes the flowers. Did I mention no mowing?
Back to your original question... I don't think solarization would be a great technique for a
garden bed location. Solarization does not improve the soil, it just kills the existing vegetation and weed seed. Maybe you could follow up the solarization with some type of cover crop to improve the soil, but then you need to do something to the cover crop to get those nutrients back in the soil. That means a few seasons until the the soil is really ready to grow anything.
If you want to start garden beds, seems like deep mulch or hugelculture might be better approaches.